Trolls are creatures that can be employed by goblins (provided they have access to them) and are used in sieges to destroy doors and other buildings. They have a pale blue blood which can stain masonry walls rather oddly when combined with their red-blooded goblin masters.
Although they cannot be butchered without modifying the game, their meat and skulls (as totems) are unusually valuable. In an unmodified game you can get their bones and skulls by leaving their corpses to rot away.
[CREATURE:TROLL] [NAME:troll:trolls:troll] [TILE:'T'][COLOR:0:0:1] [MODVALUE:10] [LARGE_ROAMING][BIOME:SUBTERRANEAN_CHASM][EVIL][DIFFICULTY:2] [GENPOWER:4] [BLOODTYPE:C] [POPULATION_NUMBER:5:10] [GRASSTRAMPLE:20] [BONECARN] [SLOW_LEARNER] [LIKES_FIGHTING] [LARGE_PREDATOR] [BUILDINGDESTROYER:2] [CANOPENDOORS] [PREFSTRING:terrifying features] [BODY:HUMANOID:2EYES:2EARS:NOSE:2LUNGS:HEART:GUTS:ORGANS:HUMANOID_JOINTS:THROAT:NECK:SPINE:BRAIN:4FINGERS:4TOES:MOUTH] [SIZE:9] [MAXAGE:800:1000] [ATTACK:MAIN:BYTYPE:GRASP:punch:punches:1:2:BLUDGEON][ATTACKFLAG_WITH] [ATTACK:SECOND:BYTYPE:MOUTH:bite:bites:1:2:GORE][ATTACKFLAG_CANLATCH] [EQUIPS] [FAT:5] [ALL_ACTIVE] [STANDARD_FLESH] [HOMEOTHERM:10067] [LAYERING:50] [SWIMS_INNATE][SWIM_SPEED:2500]