ARISE, YOG SAGOFF THREAD, ARISE!
Going off the nest idea, and the horrors of the GCS.
[NEST_HOLE]: The creature digs a small hole as its nest, a 3x3 in soil with a ramp opening.
[NEST_CORNER:ABOVE/BELOW]: The creature finds a suitable niche, either aboveground or below ground, to inhabit.
[KIDNAP_ALIVE:(method):(treatment):#]:The creature will stun its prey and incapacitate them ("method", such as FORCE for continuously knocking them out, EXTRACT for poisons, or RESTRAINT for intelligent creatures like ____men; possibly WEB, for you-know-who) and take them back to a specified lair. There, they would impose a (treatment) such as TORTURE (periodic nonlethal attacks until the # is up), HOSTAGE (does nothing, held indefinitely until starved/thirst'd), KILL (at the end of the # period) or KILL_SLOWLY (arguably the worst, stretching out severe attacks until the # is up.) Great for cave horrors and semimegabeasts, and would add the interesting point of "missions" to rescue kidnapped comrades. Goes best with [NEST] creatures.
[KIDNAP_DEAD]: Would try to take corpses from your graveyards or the battlefield. Again, intended for [NEST] subtypes.
[PLANT_EATER:#]: The creature periodically (#) eats shrubs and herbs in the terrain. A normal creature like an Elk would have a low number, while potentially ruinous creatures could have a very high value to endanger your herbalism business, maybe even your outdoor crops.
[ITEM_THROWER]: Perhaps best saved for siege beasts like giants and trolls, this would require a bit of re-coding for boulders; these animals would pick up boulders, rip out trees, and hurl furniture and loose items as projectile weapons. As anyone who's played adventure mode can tell you, this can have some devastating results, especially if they get to your lead bar stockpile, or if you leave some stray stone outside.