Rules Index | GM Screen | Player's Guide

Chapter 2: Tools / Building Creatures / Design Abilities

Basics of Ability Design

Source Gamemastery Guide pg. 67
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 Gamemastery Guide pg. 67
Understanding a creature’s action economy is key for 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 gave the creature.

Reactions can help, giving the creature a way to act when it’s not its turn. See Reactive Abilities on page 69 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 Gamemastery Guide pg. 67
The effects of an ability should be appropriate to the creature’s level. For damaging abilities, that means they follow the damage guidelines on page 68. 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. Dimension door is comparable—that’s a 4th-level 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 Bestiary volume to see if the special abilities seem similar in power to those of other creatures of the same level.

Invisible Abilities

Source Gamemastery Guide pg. 68
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.