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Archives of Nethys

Archives of Nethys

Pathfinder RPG (1st Edition) Pathfinder RPG (2nd Edition) Starfinder RPG

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GM Core / Chapter 2: Building Games / Building Creatures

Design Abilities

Source GM Core pg. 123 2.0
In this step, you'll take the ideas for abilities you noted when you developed your concept and design these abilities for your creature. You can look at existing creature abilities from Monster Core and feats from Player Core and use them as is or modify them to fit your needs.

When choosing abilities, think about both the number of abilities and the diversity of abilities. Having a large number of similar abilities can make the creature tougher to run, and it probably can't use them all anyway. A diversity of abilities gives the creature different ways to act in different situations, and helps guide you as the GM. For instance, a combat creature might have one ability it uses to get into position, another to use when it wants to focus damage on a single enemy, and a third that's more defensive.

Focus Spells

Some creatures have focus spells, especially when those focus spells clearly fit a creature’s theme. Simply give the creature the focus spells you like and between 1 and 3 Focus Points (you can also allow your creature to cast focus spells using spell slots). Use the same DC and spell attack modifier as any other spell. A creature that has just 1 Focus Point is likely to cast a focus spell only once, unless it’s a recurring enemy. If the creature has plenty of spells already, you might want to skip focus spells altogether, as they aren’t as strong as top-rank spell slots.

Basics of Ability Design

Source GM Core pg. 123 2.0
There are a few principles of ability construction that you'll want to keep in mind. Some guidance for specific types of abilities will come later, but these apply to everything.
  • Respect the action economy.
  • Make sure abilities are level appropriate.
  • Avoid “invisible” abilities.

Action Economy

Source GM Core pg. 123 2.0
Understanding a creature's action economy is key to making it work in play. Remember how short the lifespan of a typical combat creature is. Including a bunch of combat abilities might mean you spend time building actions the creature will never have time to use. Narrow your selections down to the smallest and most compelling set that makes sense. Also keep in mind that special actions will compete for time with any combat spells you give the creature.

Reactions can help, giving the creature a way to act when it's not its turn. See Reactive Abilities for advice on designing these tricky abilities.

Because of PC capabilities at higher levels, creatures at those levels should get more abilities that improve their action economy. For instance, creatures that grapple should have Improved Grab instead of Grab, Speeds should be higher, and many abilities that would have cost an action at a lower level should be free actions.

Level Appropriateness

Source GM Core pg. 123 2.0
The effects of an ability should be appropriate to the creature’s level. For damaging abilities, that means they follow the damage guidelines. For others, take a look at spells and feats with a similar effect to see if they’re level appropriate. For instance, say you’re considering giving a 6th-level creature the ability to teleport a short distance. Translocate is comparable—that’s a 4th-rank spell, normally cast by a 7th-level or higher creature. That means 6th level probably isn’t too low, but the creature shouldn’t be able to use the ability more than once. You can also compare your creature to those in a Monster Core volume to see if the special abilities seem similar in power to those of other creatures of the same level.

Invisible Abilities

Source GM Core pg. 123 2.0
Avoid abilities that do nothing but change the creature’s math, also known as “invisible abilities.” These alter a creature’s statistics in a way that’s invisible to the players, which makes the creature less engaging because the players don’t see it using its abilities in a tangible or evocative way. For example, an ability that allows a creature to use an action to increase its accuracy for the round with no outward sign (or worse, just grants a passive bonus to its accuracy) isn’t that compelling, whereas one that increases its damage by lighting its arrows on fire is noticeable. These both work toward the same goal—dealing more damage this round—but one is far more memorable.

Active Abilities

Source GM Core pg. 123 2.0
Abilities a creature uses on its turn have the most flexibility and scope. You can use the Spell DC and Spell Attack Modifier table to determine active ability DCs as well as spell DCs. You can have an ability use 1 to 3 actions as needed (or be a free action in rare cases) and use just about any type of tactic. Feats, spells, and existing creature abilities provide a wide variety of examples, so look for something similar to your idea to use as a basis.

Consider how you want your creature to spend its turns. Two-action activities pretty much define the creature's turn, and single actions work best for supplemental benefits or normal Strikes. As you build out your idea of a creature's turn, don't forget about movement! A creature often needs to spend actions getting into position, especially early in a fight. This is especially challenging with melee-only creatures. You can give such creatures abilities similar to Sudden Charge or the deadly mantis's Leaping Grab.

Use 3-action abilities sparingly, as a creature can't use them if it is slowed or stunned—making a creature's coolest or most defining ability use up 3 actions might mean the creature never gets to use it. These activities should be reserved for abilities that include some movement (like Trample) or that the creature is likely to use before engaging in combat. Don't make an ability use 3 actions as a way to balance it—saying “This can be more powerful than other abilities because it is less likely to work,” is a recipe for frustration if you've made a cool ability that's too hard or even impossible for the creature to use.

Be especially careful with activities when designing boss creatures. They're likely to get targeted with the PCs' most powerful detrimental effects, get grabbed, become slowed, or otherwise have their actions restricted. Bosses need to have solid options they can use with 1 or 2 actions. This lets them use their remaining actions to get away, use a simple ability, or otherwise keep the fight dynamic.

Free Actions

Source GM Core pg. 124 2.0
Use free actions that don’t have triggers sparingly, and when you do, they should almost always be used for support or utility actions, not Strikes or movement. If you come up with a free action, consider whether it should be its own action or part of a combo, such as drawing a weapon and attacking. In cases like the latter, you might be better off making a single action that allows the creature to draw a weapon and then Strike.

Damage-Dealing Abilities

Source GM Core pg. 124 2.0
If a special action is a single action with only one target, you can often set damage using the Strike Damage table. If it uses more than 1 action or requires setup in some way, it might deal higher damage than is typical; often, you can just use the extreme column in these cases.

For abilities that deal damage in an area, use the Area Damage table. These numbers are based on a 2-action activity (e.g., most damaging spells). Single actions should deal much less damage. An ability that has another significant effect, like applying a condition, should deal less damage; for this, look at the damage for 2 or more levels lower, and judge which value would best match based on the severity of the additional effect. These abilities typically allow a basic saving throw. The table includes values for unlimited-use abilities (ones that can be used at will) and limited-use ones (which can be used once or, like dragon breath abilities, once or twice but not on consecutive turns).

You can use the dice given or generate your own expression based on the damage in parentheses, as detailed in the Strike Damage section. If a high-level effect has a small area compared to similar abilities, you could have it deal more damage.

Table 2–12: Area Damage

LevelUnlimited UseLimited Use
–11d4 (2)1d6 (4)
01d6 (4)1d10 (6)
12d4 (5)2d6 (7)
22d6 (7)3d6 (11)
32d8 (9)4d6 (14)
43d6 (11)5d6 (18)
52d10 (12)6d6 (21)
64d6 (14)7d6 (25)
74d6 (15)8d6 (28)
85d6 (17)9d6 (32)
95d6 (18)10d6 (35)
106d6 (20)11d6 (39)
116d6 (21)12d6 (42)
125d8 (23)13d6 (46)
137d6 (24)14d6 (49)
144d12 (26)15d6 (53)
156d8 (27)16d6 (56)
168d6 (28)17d6 (60)
178d6 (29)18d6 (63)
189d6 (30)19d6 (67)
197d8 (32)20d6 (70)
206d10 (33)21d6 (74)
2110d6 (35)22d6 (77)
228d8 (36)23d6 (81)
2311d6 (38)24d6 (84)
2411d6 (39)25d6 (88)

Defensive Abilities

Source GM Core pg. 124 2.0
Active offensive abilities usually fit creatures better than defensive abilities do. Save defense increases for creatures that are strongly defense-themed. For martial creatures, something as simple as a shield and Shield Block is usually plenty. Defensive abilities often run the risk of being invisible abilities. For examples of good defensive abilities, look at spells like sanctuary for ideas, or other spells that create interesting protective effects instead of just granting a bonus. If you do want to make a creature defensive, pick one defensive ability rather than several, since stacking up multiple defenses can make for a frustrating fight. One solid style of defensive ability is a mode switch, which causes the creature to get stronger defenses, but limits its attacks, spells, or other offensive options.

Reactive Abilities

Source GM Core pg. 125 2.0
Reactions and free actions with triggers can give a creature an impact outside of its turn. This can make the fight more interesting, but it may also be risky. It's tempting to give every creature a reaction, but that's not necessarily a good idea.

To decide whether your creature should have a reaction, first consider if the creature has the reflexes or insight to react well in the first place—for instance, an ogre doesn't have Reactive Strike because it's a big oaf. Oozes, constructs, and unintelligent creatures are less likely to have reactions than others for this reason.

Second, look at the complexity of the encounter your creature is likely to appear in. If you have a large number of creatures, skipping reactions can make the fight flow faster. A creature that's more likely to fight solo, on the other hand, might have a reaction to give it a way to continue to be dangerous amid an onslaught of attacks by the party.

When creating reactions, be careful with “gotcha” abilities—ones that punish players for making perfectly reasonable choices, for rolling poorly, and so on. If you include abilities like this, they need to reinforce the creature's core theme and the play style you want it to use in combat. For example, a creature that Strikes as a reaction when someone fails an attack roll will encourage PCs to use their actions on other tactics, rather than attacking multiple times each turn. Is that what you want? Is this dynamic essential for making the creature feel like it's supposed to? This isn't the type of ability you'd give to any old creature—only an incredible duelist or something similar.

Reactions should require something out of the ordinary to happen, or should be relatively weak if triggered by something ordinary. A reaction that triggers anytime someone tries to Strike a creature is likely to be perceived by the players as uninteresting because it's so predictable.

The best reactions should be telegraphed so when they happen, it makes sense to the players. Think of one of the core reactions of the game: Shield Block. The creature raises its shield—an obvious action the PCs can see—so when it blocks damage from an attack, that makes perfect sense. Similarly, if you made a crystalline creature, you might have it build up sonic energy in a low thrum, so when it uses a reaction to release a burst of sonic energy when hit, the players can say, “Oh, I should have seen that coming.”

Reaction Damage

Source GM Core pg. 125 2.0
Reactions should use lower damage, usually that of a moderate Strike. A reaction that deals area damage might deal low damage, though use such reactions with caution.

Constant and Automatic Abilities

Source GM Core pg. 125 2.0
Certain abilities shouldn't use any actions. Auras are a common constant ability, with frightful presence, the cinder rat's fetid fumes, and the xulgath's stench as notable examples. An aura needs a range, and if it needs a DC, you'll usually set it to the moderate spell DC unless the aura is one of the creature's defining concepts. For example, the xulgath's stench DC is significantly higher because the aura is such an iconic part of the creature.

Abilities the creature has no control over should be automatic. For example, the living wildfire fire elemental explodes into flames when it dies. It has no option not to, so this wouldn't make sense as a reaction or free action. Conversely, the Ferocity ability is a reaction because it requires the creature to give itself a last push to stay at 1 HP.

Constant and Automatic Damage

Source GM Core pg. 125 2.0
Much like for reactions, damage for a constant ability should be pretty low. Usually, this value is just below low Strike damage. Automatic abilities, like the living wildfire’s explosion ability, tend to deal moderate Strike damage or unlimited-use area damage. These abilities can deal even more if they happen only after the creature is dead or otherwise no longer presents a threat.

Skill Abilities

Source GM Core pg. 125 2.0
A skilled creature might have abilities related to its skills. The skill feats in Player Core make for a good baseline. Avoid giving your creature skill abilities that won’t matter in its interactions with PCs.