How to design Action-Oriented Monsters for dynamic, tactical encounters.
In the vast tapestry of tabletop role-playing, the monsters that inhabit your dungeons and darkened lairs are more than mere stat blocks—they are the architects of excitement, the conduits of challenge, and the beating hearts of every memorable encounter.
I’m That Italian Guy, a Dungeon Master with over two decades of experience and a TTRPG game designer.
Join me as we uncover the secrets to building action-oriented monsters – creatures that forego the traditional ‘hit and be hit’ formula to seize the spotlight with tactics, synergies, and surprises.
- Video version
- Article structure and chapters
- Part 1: Conventional vs Action-Oriented Design comparison
- Part 2: Pillars of Effective Monster Design
- Part 3: Let’s Build a Boss monster
- Part 4: Non-boss action oriented monsters
- Finishing Touches
- Free Adventure “Echoes of the Void”
Video version
- Monsters and Background Art: Lion Banner Games
- Battlemaps: Borough Bound, Dungeons of Drakkenheim
- Music and SFX: Tabletop Audio, Flame Sound, Chosic, Pixabay, Videezy
Article structure and chapters
The article is split up into chapters, so feel free to skip ahead if you are already familiar with certain concepts!
- In the first part, we’re having an overview of Action-Oriented Design and checking out two Skeletons—one more conventional, and the other with an Action-Oriented vibe.
- Next up, we’re going to review and discuss the Pillars of 5e monster design. We’re talking offense, defense, and keeping the action economy solid but not overwhelming.
- In the last two parts, we’re going to build a Boss monster and its minions, according to the principles discussed in the previous parts.
- Jump to the end to grab a free one-shot adventure featuring the monsters we’re designing, a free battlemap, and VTT resources for online play!
What is Action-Oriented Design
In simple terms, Action-Oriented Design means we’re creating monsters that can do more—both in terms of quantity and quality. Their stat blocks get a boost in the action department, giving them something to do with their bonus actions and reactions. This broader range of options allows the designer to create synergies and incorporate tactical elements right there in the monster’s stat block.
But is that all? Well, kinda. With a variety of actions, these monsters pack more personality—they express who they are through this improved action economy. It also adds a layer of back-and-forth for players—can they counter the monster’s tactics? And let’s not forget, it gives Dungeon Masters more cool stuff to play around with—DMs are players too, after all!
Part 1: Conventional vs Action-Oriented Design comparison
Now, let’s see how this plays out when facing a similar creature: one designed conventionally and another embracing Action-Oriented Design.
The Dungeon Master sets the scene—a party weaving through desolated ruins, torchlight flickering in a chilling wind, when suddenly, skeletal remains of long-gone adventurers rise to attack!
A classic scenario – a low level party against a group of Skeletons.
It can do two things: attack with a shortsword; or attack with a shortbow. Both are +4 to hit and they both deal 1d6+2 points of piercing damage. The Dungeon Master gives us the lowdown, describing its appearance and highlighting its vulnerabilities and immunities. Yet, beyond its looks and resistances, its identity feels somewhat generic. We could be facing a brittle boned goblin that has been dosing with cobra poison their whole life and the stat block would be mostly identical.
Now, let’s shift to an Action-Oriented monster.
At first glance, it seems similar, even sharing identical attack actions. But a deeper dive reveals its uniqueness. This stat block tells us we’re dealing with a monster that refuses to stay down—understandable since it lost all its meat and is still kicking! With Elite Recovery, it automatically shakes off a Condition each turn when below half its maximum hit points. It boasts more hit points than a regular ¼ CR monster (double the amount of the conventional skeleton, in fact), maintaining vulnerability to bludgeoning damage but “simulating” a resistance to other damage types due to increased HP. The crucial difference? It’s a resistance that doesn’t frustrate players; no one wants to roll and be told they inflict a measly 2 points of damage. The Conventional skeleton’s low hit points ensure it will encounter a swift demise no matter the weapon, making its resistance irrelevant. But you’ll definitely see a fighter switch to their mace when facing this one!
Incidentally, the majority of Action-Oriented monsters were crafted during the later stages of the 5e development cycle, leading to this kind of “player-friendly” and more elegant approach to design. Back to our stat block!
The more inquisitive of you may have noticed that the Four-Armed Skeleton has, in fact, four arms. Unsurprisingly, the stat block reflects this by giving this monster an extra attack as a bonus action, whether with sword or bow. It also allows the Skeleton to take multiple reactions due to its Reactive Arms trait, further underlining the relentless nature of this monster.
Now, some may remark, “But TIG, this seems like a minor addition.” Indeed, the stat block itself is fairly simple. However, the first time the party wizard attempts to move away from a Four-Armed Skeleton confident that the Barbarian has already “used” its reaction, a subtle yet crucial shift occurs. Something unexpected, yet entirely foreseeable in hindsight—something that makes players go “oh!” with either a grin or a grimace.Something imprinting the encounter and the monster into the players’ collective memory. Next time they face a Four-Armed Skeleton, they’ll remember.
There’s another subtle element in this creature’s design. It’s not merely about having 3 attacks instead of 2—the additional one is a bonus action. Why is this important? A bonus action represents a discrete quantity of a monster’s action economy and acts as a balancing factor in its design. Consider this: the Four-Armed Skeleton is fighting alongside a Necromancer capable of bestowing them a defensive feature requiring a bonus action to be used. Now, choices need to be made—utilize the extra attack or opt for the added magical defenses. Or let’s say that someone casts Slow on the Skeleton – if they just had 3 attacks on their stat block, they would still be able to make all of them.
Part 2: Pillars of Effective Monster Design
So, is the solution simply to layer more actions and reactions onto existing monsters to transform them into Action-Oriented creatures? It’s a bit more nuanced than that. We still need to stick to the fundamental Pillars of balance.
So, let’s dive into some aspects that, while not exclusive to Action-Oriented Design, are nonetheless crucial components of crafting a 5e monster and play a vital role in the overall design process.
Based on its Challenge Rating, a monster should present a certain level of offense to challenge the players; it should have adequate defenses to thwart their attacks; and its action economy should be robust, without slowing down the game to a crawl or overwhelming the players.
Determine the Challenge Rating
Before you do anything else, you should start by picking a Challenge Rating for your monster. This decision essentially establishes the monster’s power level relative to the players. All the subsequent elements we’ll design revolve around this decision.
For now, we are going to stick to a generic rule of thumb:at Tier 1, especially before level 3, players are pretty squishy. But at level 5, things get spicy as they usually get a second attack or level 3 spells. After that, it’s a steady power climb. The amount of PCs is a party is obviously an important part of the equation; it is customary to balance creatures around the average party size of either four or five player characters. In this series, we are assuming a party of 5 as our baseline.
By following this (extremely simplified) approach, and assuming a single monster vs the party, we can say that:
- Level 1 characters will mostly face enemies up to CR 1.
- PCs above level 1 but below 5 should tackle enemies not higher than their level +2.
- Tier 2 characters can handle enemies up to their level +5.
- Tier 3 and 4 PCs can take on monsters up to their level +7 and even more. If you’re designing a monster for a specific campaign, knowing when the party will face this creature is key. Of course, the numbers change if you’ve got more monsters in an encounter (we’ll get into that later).
And if you’re just crafting an enemy without a specific party or campaign in mind, you can still use this simple guide to guess the average power level for a creature of a specific CR.
Balancing encounters is a whole other beast and deserves its own chat in another video. And if you want a more in depth discussion on this topic, you can’t really go wrong with The Lazy DM’s Forge of Foes (this is, in fact, an excellent resource for building action oriented monsters in general!).
But for today, the big takeaway is this: pick a CR before you start your monster design journey.
Monster Building exercise – CR
Now, let’s roll up our sleeves and craft an example to illustrate this concept. Our party? A seasoned team of five level-five adventurers. To face them, we’re going to build a boss monster with a trio of sidekicks.Since this is a boss fight, we want it to be quite challenging – so the Boss is going to be a CR 7 monster and its underlings are going to be CR 2.
We are also going to pick an identity for our adversaries. Crafting a memorable theme is crucial in monster design, and it holds even more significance when developing an Action-Oriented creature – The identity should emerge through its name, its art and the actions in the stat block, shaping a memorable and engaging villain. Keep an eye out for a future video dedicated solely to this (quite expansive) topic!
We’ll dub our Boss monster the “Void Invader”. It is going to be an otherworldly creature, with the power to rupture reality and draw in Void Spawns from the space between worlds – its underlings in this fight. This is going to be a Deadly encounter for a five player party of level five adventurers.
Expected Values based on CR
I emphasized the CR selection because in 5e, there’s a structured reliance on an expected average value for a creature’s stats, all determined by its Challenge Rating.
A good example of this is something in 5e called “bounded accuracy”. It’s basically the game’s way of keeping things in check and avoiding crazy power creep. Unlike earlier editions, where numbers would skyrocket with each level, 5e maintains a more restrained scaling system. Whether it’s the chance to hit or the DC of a creature’s effects, the increments are more moderate and, more important for our design needs, more linear.
This implies that nearly every aspect of a monster’s design has a measurable, expected average value linked to its Challenge Rating. A couple of excellent resources for this kind of math are BLOGOFHOLDING.COM’s Monster Manual on a Business Card and Level Up: Advanced 5e’s DESIGNING MONSTERS section of the Monster Menagerie.
Both are fairly similar – which is unsurprising since they were both based on existing 5e official monsters and, as far as I know, both were written by Paul Hughes. Forge of Foes also provides its tables and rules for expected monster stats based on CR.
Expected Offensive Capabilities
Once you have established the CR of your monster, the first step is figuring out how good it should be at landing attacks and how tough its abilities are to resist. This boils down to two key factors: the monster’s proficiency bonus and how high their main attack Ability (like Dexterity or Charisma) is.
As a rule of thumb, a CR1 creature typically has a +4 to hit with attacks (a +2 proficiency bonus and +2 from their main attack Ability). The DC of their effects with a save average around 12 (8 base +2 proficiency bonus and +2 from their main attack Ability). These numbers increase somewhat linearly, with a bump every two CRs or so.
Now, let’s talk about damage. A quick rule of thumb is to start at 10 damage per round for a CR1 creature and increase by 5 damage per round for each CR increment.
Keep in mind, these are average values, and monsters may deviate based on their role, fantasy, and design. This is where the beauty of Action-Oriented design shines—two creatures might have a similar attack ratio and damage pattern, but their approach could be wildly different, injecting variety into combat – a crucial aspect in a game like Dungeons and Dragons that heavily relies on this type of encounter.
Monster Building exercise – Offense
We’re sticking close to the averages to showcase how you can craft unique monsters from similar building blocks.Our Void Invader is a CR 7 creature, so we know it is going to have:
- A +3 proficiency bonus and a “good” ability score with a +4 modifier.
- Its attacks are going to have a +7 to hit and the DC for his effects is going to be 15.
- It is going to have an average damage per round of 40. The Void Spawns are CR 2 monsters, so their offenses are going to be as follows:
- +2 proficiency bonus and +3 ability modifier.
- +5 to hit, DC 13.
- 15 damage per round on average.
Expected Defensive Capabilities
Based on a Monster’s CR we can also extrapolate their average Hit Points and how high their Armor Class and “Good” Saves are going to be.
As a general rule of thumb, a CR 1 monster will have around 30 hit points and this number climbs by roughly 15 for each CR above one..
When it comes to their “Good” saves—the ones benefiting from both their “Good” Ability score and proficiency bonus—you can expect them to match their attack bonus or fall slightly below. So if a creature boasts a +7 to hit, their good saves will likely be either +7 or +6.
Now, let’s tackle Armor Class. The general rule is to begin at AC 13 or 14 for a CR 1 to 3 creature, adding +1 every three CRs. Among the “expected” values we’ve explored, Armor Class tends to exhibit more significant deviations based on a monster’s design and fantasy. For example, a CR ⅛ Guard may sport 16 AC, while a CR 8 T-Rex might surprisingly have a modest AC 13.The important thing to remember is that bounded accuracy is a thing in 5e and that missing most of your attacks is not fun – it’s usually better to give monsters increased health or more interesting defensive abilities instead of just bumping their AC sky-high.
Monster Building exercise – Defense
We are also going to stick to average values more or less when it comes to our villains’ defenses. The Void Invader will have:
- Around 120 hit points.
- Good saves in the +6 to +7 range.
- An AC of 15. The Void Spawns, at CR 2, will have values similar to these:
- 45 hit points.
- Good saves around +4 to +5.
- AC 13.
Action Economy Balance
Action economy boils down to the number of actions a side can take in a round – it is like the currency of combat in 5e and, as such, it is a critical component of monster and encounter balance. You can picture it as a resource that defines the number of moves each side can make in a round. The more moves your party has, the better their chances, and conversely, the more moves the monsters have, the tougher the encounter becomes.
Now, conventional monsters often lag in the action economy game, sticking to a simple routine—one action per turn, usually one or more identical attacks or a flashy ability. But in the late stage of 5e development, where player classes offer a smorgasbord of choices for actions, bonus actions, and reactions, players facing similar numbers of monsters gain a mechanical edge.
To address this action imbalance in conventional design, the usual tricks involve making monsters “mathematically” superior to PCs (dealing more damage or being tougher to hit) or tossing more monsters into the mix. Both have their pitfalls, though. A high-damage monster could – given bounded accuracy and the innate low-high swing of a dice based damage system – swiftly take out a single PC, leading to less fun for the affected player. Conversely, adding more combatants can turn the fight into an admin nightmare, with loads of individual attack rolls and hit point tracking.
By applying elements of Action-Oriented design to our monsters, we can somewhat balance the action economy of combat, while making things more interesting for our players. However, we must tread carefully and consider “how many things” our monsters can do in a turn, especially when designing monsters that act in groups. This helps avoid overwhelming the players with the monsters’ improved action economy and prevents the combat from dragging on excessively.
Compared to other Pillars of Effective Game Design, action economy has more nuance, making it challenging to abstract as a simple numerical value. A good rule of thumb is that, when facing low-level adventurers, monsters should be able to reliably do only a couple of things each turn. Then, their action economy should improve around level 5 and every 5-6 levels after that – more or less each time the PCs’ action economy improves. This doesn’t mean their stat block shouldn’t have more things—just that some of them should be situational. For example, the Four-Armed Skeleton only gets its Recovery trait when below half maximum hit points, and its reactions are limited by the fact that the PCs may not trigger a single one of those.
The other thing to remember is that boss monsters – or any monster that is supposed to be a challenge for a full-fledged 5-member party – are affected by the action economy imbalance the most. This is where legendary or lair actions come in: by giving a Solo monster a chance to act outside of their turn, we level the playing field a bit.
Monster Building exercise – Action Economy
We want our Big Bad Evil Guy, the Void Invader, to be the main event in this showdown, so we’re tailoring its action economy accordingly. It’ll boast a couple of main actions, a bonus action, and a reaction. Given that it’s bringing some friends into the mix, we’re skipping Legendary Actions and opting for Lair Actions instead. Lair Actions are a solid choice when the odds are nearly even, maintaining that back-and-forth rhythm between the party and the monsters. Legendary Actions shine when the party faces a lone villain, but keep in mind that high-level bosses might need to have both to stand a chance against stronger characters!
We are going to further refine this next, when we start writing down the full stat blocks for our enemies.
Part 3: Let’s Build a Boss monster
What do we know about the Void Invader? It is otherworldly, it punches holes in reality, it has creepy tendrils and a big maw at the center of its chest. How does his otherworldliness manifest?
Void Invader
Large aberration, chaotic evil
Armor Class : 15 (natural armor)
Hit Points : 126 (12d10 + 60)
Speed : 40ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 18 (+4) | 9 (-1) | 20 (+5) | 19 (+4) | 16 (+3) | 13 (+1) |
Saving Throws : Constitution +8, Intelligence +7, Wisdom +6
Skills : Athletics +7, Arcana +7, Perception +6
Damage Resistances : Poison, Necrotic
Damage Immunities : Psychic
Condition Immunities : Grappled, Poisoned, Restrained
Senses : Darkvision 120 ft., Passive Perception 16
Languages : Deep Speech, telepathy 120 ft.
Challenge : 7 (2,900 XP)
Reality Shift (3/day). If the Invader fails a saving throw, it can choose to succeed instead; when it does so, it loses any temporary hit points it currently has and it can’t use its Chest Maw attack until the end of its next turn.
Reality Riptide. The Invader projects a strong un-reality field and its mere presence can torn asunder the fabric of reality when it senses its prey. When it rolls for initiative, the Invader opens breaches into the Void at three empty spots that it can see within 60 feet, shattering reality in a 10-feet-radius area centered around each spot. A creature starting their turn in one or more of these areas must succeed on a DC 15 Wisdom saving throw or be restrained until the start of their next turn. A creature restrained in such a way can use a bonus action to push their mind to its limits, removing the restrained condition and taking 14 (4d6) psychic damage. The breaches persist for 1 hour or until the Invader rolls for initiative again.
Actions
Multiattack. The Invader makes two Razor Grip attacks. It can replace one of these with its Synaptic Tendrils action if available.
Razor Grip. Melee Weapon Attack: +7 to Hit, reach 10 ft, one target, Hit: 11 (2d6+4) slashing damage and if the target is a Large or smaller creature it is grappled (escape DC 15)
Synaptic Tendrils (Recharge 5-6). The Invader probes the mind of each creature of its choice that it can see and that is within an area affected by Reality Riptide. Each of these creatures must make a DC 15 Intelligence saving throw or be stunned until the end of their next turn. A creature that fails the save can instead choose to take 22 (5d8) psychic damage and immediately remove the stunned condition.
Bonus Actions
Chest Maw. Melee Weapon Attack: +7 to Hit, reach 5 ft, one creature, Hit: 13 (2d8+4) piercing damage and the Invader gains as many temporary hit points. Can only be used against a creature the Invader is grappling or against a creature within an area affected by Reality Riptide.
Rections
Void Jaunt. When the Invader is damaged by an attack or spell, it can use its reaction to teleport to an empty spot that it can see within any area affected by Reality Riptide. Any creature grappled by the Invader is teleported with it, if it chooses so.
Lair Actions
The Void Invader can only take these actions when it is in an area where the space between worlds is thin. On initiative count 20 (losing initiative ties), the Void Invader can take one lair action to cause one of the following effects; the Invade can’t use the same lair action two rounds in a row:
Spatial Anomaly. A creature the Invader can see within 120 ft. must make a DC 15 Intelligence saving throw or take 7 (2d6) psychic damage and be teleported up to 30 ft to an empty spot on the ground of the Invader’s choice that it can see. On a successful save, the creature takes half damage and is not teleported.
Veil Breaker. Until the next initiative count 20, the area of shattered reality around a Reality Riptide breach is increased by 10 ft. to a 20-feet-radius area centered around each spot. During this time, a creature standing inside two or more of these areas at the same time makes the Wisdom saving throw against the effects of Reality Riptide with disadvantage.
Dimensional Maw. The Invader makes a Chest Maw attack against up to two creatures. If a creature is within an area affected by Reality Riptide, the Invader can make the attack as if it was within reach as long as it can see the creature.
Core Stats: Beyond the Tentacles
While these might be the driest aspects of a design task, Core Stats play a crucial role in informing both the GM and players about how a monster fundamentally interacts with the game world. Can it see in the dark? Can it communicate with the players? Is it agile or cumbersome? What kind of environment suits it best?
Carefully crafting a monster’s core stats allows us to signal its strengths and weaknesses. By aligning these stats with the fundamental aspects of the monster’s design, we can infuse more flavor into it.
From a mechanical standpoint, unless dealing with a specialized creature, having a well-rounded core block is usually a good idea. This can be achieved by balancing strong and weak points or by creating an all-around balanced stat block.
Looking at our Invader, the concept art suggests it is powerfully built, and we can assume its otherworldly nature grants it superhuman resilience. However, its alien frame is poorly adapted to our world—its movements are erratic and jarring, as if in a constant struggle to maintain its form stable in this reality. Its mind proves to be as formidable a weapon as its claws and teeth, perhaps even more so.
Acting out of initiative.
We want our Boss monster to be a visible presence throughout the fight, and this means having it act outside of its normal turn.
Occasionally, a monster centers around a crucial feature that shapes the entire encounter, setting up a scenario with a buildup and a payoff. However, the 5e initiative system poses a challenge: a Boss might roll poorly, delaying its actions significantly in the first turn. One potential solution, currently under exploration in One DnD, involves an ability that activates when a creature rolls for initiative.
Our Invader’s first Trait plays a central role in shaping its entire stat block—many of its abilities center around the breaches it creates and their reality-bending effects. We want our Invader to reliably deploy these at the start of a fight, but since Dexterity is its weak spot, the Invader is going to act at or below initiative 10 more often than not. By triggering this action when it rolls for initiative, we ensure that the Boss gets to do something flashy at the start of the combat, providing a more dynamic and engaging opening to the encounter while giving the players a chance to react before the Boss takes its turn. There is an interesting element to the saving throw, but we’ll talk more about this a bit later.
Another way to have the Boss feel more dramatic and impactful is to give it Lair Actions.
We aim for these actions to pack a punch equivalent to a full monster action, defining our Boss with flashy and memorable abilities. They should also be flexible enough that a monster will be able to reliably use all of them in a single fight.
Now, the catch with Lair Actions is their dependence on the monster being in some form of Lair. While this can be somewhat abstracted (as per our example), it poses limitations, preventing the monster from reaching its full potential outside the Lair’s conditions. On the flip side, it opens a window for a clever party to disrupt the monster’s effectiveness by luring it out of its Lair.
A noteworthy alternative, inspired by MCDM, is the concept of “Villain” actions. These operate similarly to Lair actions, but a powerful Boss monster inherently possesses them as part of its action-oriented design. You can learn more about this by checking out this video by Matt Colville, or their excellent Flee Mortals and Where Evil Lives 5e supplements.
Spatial Anomaly: The first Lair Action on the Invader’s stat block is a combination of utility and offense. Intelligence tends to be a disregarded save, as mind-affecting abilities typically target Wisdom or Charisma. Our goal is to make this otherworldly entity feel truly “out of this world” – this is not your average magic user, but an inscrutable, vast, cold, alien mind. From a mechanical standpoint, this action allows the Invader to strategically relocate a pesky Sentinel fighter near a breach in reality, or to lure a tasty snack from the backlines next to itself.
Veil Breaker: The second of the Invader’s Lair Actions allows it to play a nasty trick against those PCs that are standing dangerously close to the breaches, thinking they are safe. Tactical positioning is often an overlooked element in 5e and but it is quite relevant to this encounter. The surprise element adds a feeling of suspense—Will the breaches grow more? Will they move? It keeps players guessing and amps up the tension.
As for the third Lair Action, we’ll hold off on discussing it for now, but we’ll circle back to it shortly for reasons that will become apparent.
Monster Bread and Butter: Actions
This part of a monster’s stat block details its primary attacks, typically consuming a significant portion of a monster’s damage budget, especially in the case of non-boss monsters.
Multiattack: This is going to be an omnipresent action in most monster stat blocks, with higher-level monsters featuring three or even four attacks as part of their Multiattacks. We want our monster’s offense to be split up into several discrete chunks, because of two reasons: we can use it to split damage over multiple targets, avoiding a player being pasted by a single 40 damage attack; and it allows the GM more flexibility, when several options are provided. In this case, the profile is simple enough and the monster is going to use two Razor Grip attacks whenever Synaptic Tendrils is not charged.
Razor Grip: Looking at the concept art, we see that our Invader has multiple spiked and clawed limbs. we’ll provide it with two straightforward attacks that also carry the added effect of grappling the target upon a successful hit. This will allow the Invader to exert some level of control on the players’ positioning, granting it the ability to drag one or more grappled players into an area affected by a reality-shattering breach. We will allocate roughly half of the Invader’s damage budget to these attacks.
Synaptic Tendrils: It is customary for a Boss monster to have at least one scary area of effect attack with some kind of limited usage – a sorcerous fireball, a dragon’s breath attack and so on. These abilities allow the monster to flex its muscles in a flashy way; when these abilities come with a recharge roll, the players should be engaged in the result! In our case, our Invader has some mind tendrils to go with the physical ones crawling out of its face. It is also a save or suck effect…or is it?
Save or Suck (the fun out of a game)
Save or Suck effects are a staple of D&D – from the lowly hold person, to older edition insta-kill spells like Finger of Death. In 5e, the latter has been somewhat toned down, but non-lethal save or suck spells are alive and well. And while powerful monsters can avoid effects like Banishment with Legendary Resistance, players lack that luxury.
There are two schools of thought on player agency in 5e, and I firmly believe that “not being able to act on your turn” sucks. Even with experienced players, it may take 15 to 20 minutes before someone gets a turn; if all they can do is say “I am stunned” and pass, it means 30 to 40 minutes before they can play.
A good alternative is to offer players a choice, restoring some agency. Here, players can choose between a severe condition and significant damage—enough to bring most level 5 characters below half their maximum hit points. If there was any doubt, now the players know to avoid areas affected by Reality Riptide!
These limited usage effects allow a monster to have “power turns” that break free from the normal constraints of its damage budget. We account for this by replacing one of the Invader’s regular attacks and having it deal less than its full 40 points of damage on “off turns” when it lacks access to this action.
The Cherry on Top: Bonus Actions and Reactions
While Actions form the core of a stat block, Bonus Actions and Reactions help complete a monster’s profile with more specialized or situational abilities. Depending on the monster’s nature, these additions can enhance its offense or defense, or offer additional utility through buffs for allies or debuffs for enemies.
The Void Invader is a monster with standard defenses – Armor Class, Hit Points – that relies on precise positioning for a lot of its abilities to function properly and notably lacking ranged attacks. Void Jaunt enhances both its survivability and mobility, offering a versatile option for defensive maneuvers and offensive tactics.
There is a jagged elephant in the room: looking at the concept art, we can see that the Invader has a large mouth filled with pointy teeth on its chest. We are going to use our allotted Bonus Action to add a situational but more powerful attack to the Invader’s profile; this also comes with the added benefit of adding a bit of quasi-healing to the monster for added survivability – Boss monsters tend to be a bit tougher than a regular creature of the same CR.
When calculating the budget for a situational attack, it is customary to only count half to three quarters of its expected damage – since it will only be available on certain turns. In our scenario, as we anticipate it to be almost always available, we’ll lean towards the upper end and treat this as a 10 damage attack.
We can now go back and fill in the third Lair Action. Dimensional Maw overrides the limitation of Chest Maw, giving the Invader another powerful “aoe” attack. While still technically situational, the Invader is almost always going to be able to make both attacks, so we consider this a 20 damage action. This number aligns with the damage profile of Synaptic Tendrils, and this is no mere coincidence.
Flow, Tactics and Combat Math
When planning complex, action oriented monsters, the goal is to offer the GM tactics that naturally unfold as the monster deploys its abilities—a Lair Action that powers up an attack that, in turn, enables a bonus action. However, particularly if we’re designing this monster for a module or adventure, providing a breakdown of its common tactics can serve as a handy guide for the GM running the encounter.
In the case of the Void Invader, it may look something like this:
- 1st Round: Veil Breaker + 1 Razor Grip + Synaptic Tendrils + Chest Maw = 43 average damage
- 2nd Round: Dimensional Maw + 2 Razor Grip + Chest Maw = 52 average damage
- 3rd Round: Spatial Anomaly + 2 Razor Grip + Chest Maw = 39 average damage
We are going over budget by about 25% on a round, which is within acceptable margins for a Boss monster with Lair Actions. Keep in mind, this isn’t set in stone – Synaptic Tendrils might recharge more frequently than the anticipated 33%, or the GM may have a high damage turn:
- High Damage Turn: Dimensional Maw + 1 Razor Grip + Synaptic Tendrils + Chest Maw = 63 average damage
But as long as the damage profile is properly balanced and its actions have some form of “cooldown” – in our case, the recharge roll on Synaptic Tendrils and the constraint we have set on using the same Lair Actions twice in a row – the GM can follow up with a lower than average turn:
- Low Damage Turn: Veil Breaker + 2 Razor Grip + Chest Maw = 32 average damage
When we average out all these potential turns, the expected damage per round for our Boss monster is 45.8, well within what can be expected by a CR7 Boss monster – especially considering that the damage is split between 3 to 5 sources – and, as such, can be spread over different targets.
There is an additional floating 7 damage to be budgeted when players try to break free from a Reality Riptide. But, taking this damage likely means they’re safe from the Invader’s tougher moves—a bit of a trade-off. In the end, both options likely even out damage-wise. Considering the added penalties of being restrained and how multiple control effects can stack, it’s a balanced choice.
When designing a monster we can’t account for all the edge cases. Some groups prefer their GMs to push the boundaries of combat, targeting squishy characters while ignoring the heavily armored ones unless they are forced not to. On the other hand, other groups enjoy a more relaxed experience, where monsters go after player characters that enjoy trading blows for role-playing purposes. Personally, I like to mix it up, tailoring the experience based on the flavor of the monsters; for instance, a group of bounty hunters might employ shrewd tactics, while mindless undead may adopt a straightforward “first come, first served” approach.
The golden rule is that, over a three-round period, the monster should maintain a somewhat consistent damage profile while showcasing its full arsenal. If we only account for the “suggested” first three rounds, the average is 44.6 and the Invader gets a chance to employ all of its abilities.
But why specifically care about three rounds?
The “Three Rounds” Rule and Legendary Resistance
The Void Invader, being a Boss monster, needs to make a significant impact over three rounds, as most combat encounters are balanced around this timeframe.
In 5e, combat follows a “rocket tag” resource expenditure and damage profile. Both sides spend their resources early in a challenging encounter, and the bounded math ensures that most effects hit their mark. Players spend action surges, smites, and high-level spell slots, while monsters use abilities with limited uses or on a recharge. After three rounds of this intense firepower, the combat is typically over or has an expected outcome.
To ensure a Boss monster remains effective for three rounds, a common solution is to grant it Legendary Resistance. This, coupled with immunities, prevents a single save-or-suck spell from prematurely ending the combat, resulting in a less dynamic fight. However, when a monster uses Legendary Resistance, it creates a “low point” in the combat enjoyment for players, as there is no discernible difference from the monster simply making its save, and resources are spent to no avail.
While a monster will theoretically run out of Legendary Resistance, this usually occurs after the expected three rounds.
That’s why we’ve given the Void Invader a trait like Reality Shift. This allows the monster to maintain its ability to interact with players in a fun way, while players also gain a tangible benefit when it fails a save against a nasty effect.
If we go over the Combat Math we were examining before, we can see that without access to its Chest Maw, the Invader’s damage per round is cut down by an average of 10, bringing its expected average damage on a round when it has benefited from Reality Shift to 34 damage.
Part 4: Non-boss action oriented monsters
Now that we have our Boss monster, it is time to build some underlings for the encounter. While not as powerful or complex to run as the Void Invader, they are still going to benefit from an action oriented design. This approach ensures they synergize with the boss, allowing tactical elements to emerge organically when they act, in a way that both challenges the players while offering them opportunities for strategic counters.
Once again, we are building this monster starting from two essential elements: concept art and a broad vision of its identity and functionality.
We know the Void Spawns are going to be as otherworldly as the Invader, so we want her alien nature to be apparent in the stat block. From the concept art, they seem to be somewhat agile, with a long tongue and with a set of massive scythe-like talons on their back. We want them to act as a force multiplier for the Boss, making it easier for the Invader to keep people inside the areas affected by Reality Riptide.
Like we did with the Invader, we’ll mainly stick to average values suitable for the Spawns’ CR – showcasing how, through action-oriented design, we can build a distinctive monster even when working with somewhat standard numbers.
Void Spawn
Medium aberration, chaotic evil
Armor Class : 13 (natural armor)
Hit Points : 39 (6d8 + 12)
Speed : 30 ft., climb 30 ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 14 (+2) | 16 (+3) | 14 (+2) | 6 (-2) | 12 (+1) | 6 (-2) |
Saving Throws : Dexterity +5
Skills : Stealth +5
Damage Resistances : Psychic
Condition Immunities : Grappled, Restrained
Senses : Darkvision 60 ft., Passive Perception 13
Languages : –
Challenge : 2 (450 XP)
Fractured Reality. The Void Spawn’s nature intrinsically distorts perception, inducing confusion and disorientation. When the maximum value is rolled on at least 1 damage die for an attack made against the Spawn, the damage of the attack is halved.
Actions
Multiattack. The Void Spawn makes two Prehensile Tongue attacks.
Prehensile Tongue. Melee Weapon Attack: +5 to Hit, reach 15 ft., one target, Hit: 5 (1d4+3) bludgeoning damage and if the target is a Large or smaller creature it must make a DC 13 Strength saving throw or be pulled up to 15 ft. towards the Spawn and be knocked prone.
Bonus Actions
Hobbling Talons. Melee Weapon Attack: +5 to Hit, reach 5 ft, one prone creature, Hit: 7 (1d8+3) piercing damage and the target’s speed is halved until the end of its next turn.
Non-boss Monsters: One of Many
When building a monster that is going to appear in multiple copies in the same encounter, the design approach becomes a dance between efficiency and engagement, especially when sharing the stage with a complex Boss.
The focus shifts from mere combat prowess to streamlining admin aspects – simplifying the tracking of their effects and ensuring swift turns while keeping the excitement of action-oriented elements.
In this context, achieving “Elegant Design” implies striking a delicate balance between granularity and variety on one side and minimizing potential confusion or game slowdowns on the other.
Let’s have a look at a Trait for the Void Spawn, examining the decisions that lead to its final optimized (and hopefully engaging) version.
Elements of “Elegant Design”
One of the key tenets of Elegant Design revolves around standardization and the strategic reuse of existing systems. This makes it easier for everyone to remember how specific effects work and to keep things consistent. An often optimal way to achieve this result is to simply reuse an existing effect the players may already be familiar with.
When designing a defensive trait for the Void Spawn, rooted in its surreal nature, the first solution was to simply give it a Mirror Image effect.
Opting for the Mirror Image effect had its perks—it saved time by tapping into players’ familiarity and kept the trait description concise. However, it introduced new challenges. It saddled the combat with multiple additional rolls; the GM had to track each Spawn’s remaining images; different thresholds for the d20 rolls further complicated matters.
This had the immediate benefit of using an effect the players were already familiar with, cutting down on explanation time; while keeping the trait’s description brief. It, however, ran into a bunch of other issues. First of all, the multiple additional dice rolls would slow down the combat; second, the GM would have to keep track of how many images each individual Spawn had left; finally, each image count has a different d20 roll threshold for an image to be struck.
While reusing an existing effect could usually be considered Elegant Design, in this case it proved otherwise. Thus, Fractured Reality was revisited for a more refined solution.
This new version simplified image tracking and roll thresholds, but it still had the same setback of slowing down the game with multiple extra rolls. It was also quite a powerful ability – granting the Spawn a consistent 50% damage reduction against attacks. Third time’s the charm?
This version addressed the persistent 50% damage reduction but brought its own set of challenges. The GM’s task of tracking each Spawn’s reaction usage was a bit unwieldy. And considering the goal of having Spawns assist the Invader in controlling PC movements, preserving their reactions for Attacks of Opportunity was crucial. This is how we got to the final version.
This version of Fractured Reality satisfies all our design goals: it is economous in its admin time, not needing any additional roll; features concise text, doesn’t burden the GM with additional tracking, keeps the Spawn’s reaction available; it can trigger multiple times, but it is not too powerful.
In the end, it preserves the thematic fantasy of a creature manipulating reality and fulfills its role of providing situational damage reduction. To offset this, I’ve slightly reduced the Spawn’s hit points by about 15% from the expected average value of 45.
Balancing effectiveness and speed
Making the Void Spawn easier to run than the Invader is a priority, but we still want it to be interesting for the players to fight and to work well with the Boss’s abilities.
We gave the Spawn two attacks to spread out the damage and increase the chances of triggering the extra effects of Prehensile Tongue. The repeated saves might slow things down a bit, but I’m less worried here, for a couple of reasons: it’s an interactive roll that gives players something to do, not extra work for the GM; and it’s like a one-on-one challenge against a monster rather than an abstracted roll. With an expected average damage of just 10 per round (even with the potential for two minor conditions), we’re keeping a Bonus Action in reserve to add some action-oriented elements to the Spawn.
This attack brings the damage profile of the Spawn more in line with its expected budget of 15. Halving someone’s speed is usually an almost negligible effect, but in this specific combat – where mobility is king – it poses a much more credible threat. As a reminder, in 5e the same effect does not stack in magnitude if it is applied multiple times by the same source – so, no need to track how many times Hobbling Talons slowed the same target—keeps things simple. At the same time, standing from prone consumes an amount of movement equal to half your speed, so if someone is knocked prone and then Hobbled, their mobility shrinks to a crawl.
Synergies and Force Multipliers
A single spawn’s abilities have Internal Synergy—Prehensile Tongue knocks foes down, setting up Hobbling Talons to keep them grounded.
When multiple Spawns are fought together, their abilities have Group Synergy, enabling each other’s Hobbling Talons. They also act as Force Multipliers. Once a target is down, the next Spawn gets advantage on attacks. And a lone pull might not be a big threat, but picture three spawns dragging a victim up to 90 ft. before Hobbling them—now that’s a real challenge!
Finally, they act as a Force Multiplier for the Invader, by repositioning and pinning PCs inside the areas affected by Reality Riptide. A 5 damage attack of opportunity isn’t a big deal…but add reach, a pull, and prone near a reality-bending breach, and escaping gets tricky.
In this fight, the players will want to move around a lot and the Spawns are going to make things difficult – and hopefully fun! – for them.
This doesn’t mean that these monsters can’t be fun to fight outside of a Boss encounter. A group of Void Spawns attacking the players on their own can be a very interesting challenge with the appropriate battlemap – verticality and hazardous terrain become much more threatening when your monsters have a climb speed and they can pull PCs around with their attacks.
Finishing Touches
Peer Review (or Self Review)
No game designer is immune to biases, and even seasoned creators can have blind spots. That’s why having someone you trust review your work before progressing is valuable.
Peer review, a common practice in technical fields, helps refine a monster’s stat block, smoothing out any rough edges. What seems clear to you may need additional details for others unfamiliar with the design. Errors in math or other crucial aspects might also surface during this process.
If you lack a peer reviewer, taking a break and revisiting your work with fresh eyes the next day can be surprisingly effective. It’s surprising how things that looked well-designed initially might seem messy after you haven’t thought about them for a while. Monster Building exercise – Peer Review When I submitted the Void Invader and Void Spawns for peer review, two main elements surfaced, aside from minor clarifications and typos—appropriately, one per monster. Initially, the Invader’s Reality Riptide was one of its Lair Actions. Feedback suggested this action felt too crucial, making it the obvious choice for a DM on turn 1. While I included it as a Lair Action to ensure it triggered before the Invader’s first turn (with a -1 initiative modifier, the Invader could not possibly beat the Lair’s 20), I overlooked how this could limit the DM’s options and dampen the overall enjoyment. Thus, Reality Riptide transformed into a trait that activates when the Invader rolls initiative, and Veil Breaker took its place as a new Lair Action.
The second significant change came to the Spawn’s Prehensile Tongue attack. Originally, it was a “Melee or Ranged” attack with a reach of 10 feet or a range of 30 feet. Feedback suggested this versatile toolkit was too potent for a CR2 creature. To address this, I opted for the melee option, extending their reach slightly to enhance their ability to interfere with players’ movement and match their pull distance.
Playtesting
Once you’ve wrapped up writing and reviewing your monsters to an acceptable standard, it’s time to put them to the test against real opponents! Playtesting is crucial for addressing those edge cases and judgment calls that come with designing more intricate abilities. It helps answer questions about subtle design elements that go beyond simple math rules: Are there unexpected interactions between the monsters’ abilities? Is one ability over or underperforming? Is their theme, role, and fantasy coming through in their actions? And most importantly, are they fun to fight? Recruit players, set character creation rules, and guide your party through one or more encounters, depending on how many monsters you have to test. Ensure the feedback you gather is actionable and avoid leading questions. If possible, have someone other than you run the playtest to minimize unconscious biases – this encourages the playtesters to be frank and direct with their opinions. Playtesting and feedback collection are substantial topics that we’ll delve into in more detail in the future. For now, if you’re looking for a solid starting point, you can check out Pesto’s Guide to Testing by MCDM’s senior contract tester Spencer Hibnick. It’s available for free on itch.io.
Monster Building exercise – Peer Review
I tested these monsters in a single encounter against a 5-strong party of level 5 adventurers, including a sorcerer, paladin, rogue, cleric, and a moon druid-barbarian multiclass. An excellent way to assess how a mostly melee-focused party would fare against monsters with such an array of crowd control effects. Before the playtest, there was no option to escape the effects of Reality Riptide by taking damage, and Hobbling Talons set the speed to 0 instead of halving it. This resulted in a couple of characters spending all 5 rounds of the combat under some form of crowd control, with the sorcerer spending most of the encounter flat on their back, unable to stand up.
This is really bad, right? Well, yes and no. Even restrained, prone, and with a speed of 0, the sorcerer could cast non-attack spells without issues, launching a fireball that instantly took out one Spawn and dealt substantial damage to the Invader. The primary disadvantage was on the defensive side, easily mitigated by spells like Misty Step.
Stacked crowd control posed a more significant problem for the moon druid-barbarian. While a raging brown bear is intimidating, it’s not much of a threat if you are standing just beyond its reach. Although not the best from an optimization standpoint, a mainly melee character is a common fantasy for many players. These characters are often the sturdiest, so introducing a “take damage to break free” option felt like the right solution.
Outside of the case of a pure melee character, the players felt that the lack of true ranged options on the monsters’ side made the amount of crowd control feel more fair – the Void Invader could not simply place down Reality Riptide as a barrier and shoot over it. The monsters’ need to engage up close allowed characters with high mobility, like a dashing rogue, a mounted paladin, or a teleporting sorcerer, to leverage that advantage, employing hit-and-run tactics to their benefit.
Players particularly enjoyed Reality Riptide, feeling it added significance to positioning, especially when paired with Veil Breaker. If you remember, this was one of our design goals, so I was really happy to hear that!
After a few tweaks, the final adjustments to our monsters were made. It was time to unleash them on the unsuspecting population of a nearby town…
Free Adventure “Echoes of the Void”
In “Echoes of the Void,” the adventurers find themselves drawn into a village plagued by mysterious disappearances. As they investigate, they uncover a sinister peril involving interdimensional creatures from the Void. The source of these eldritch horrors is an abandoned tower ruin hidden within the nearby forest, where a forgotten relic weakens the veil between dimensions.
The adventurers must investigate the village and the surrounding countryside, piecing together clues to the nature of the threat and its source. Along the way, they encounter frightened villagers, haunted landscapes, and the lingering echoes of the Void’s influence.
Their journey leads them to the abandoned tower ruin, where they confront not only the Void Invader and its Spawns but also the perilous artifact responsible for weakening the barriers between worlds. To save the village and restore the fabric of reality, the adventurers must defeat the creatures and neutralize the artifact.
Download Links
- Grab the Echoes of the Void v1.2 PDF
- You can now install the Foundry Module from Foundry itself!
- The Battlemaps archive is not needed if you are using the Foundry module! However, this file comes with additional variations (day, dusk, dawn) that are not included in the module itself.
Dungeon Dynamics 
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