Chulls - Capaloptocus/wordsofradiancemod GitHub Wiki
Chulls are creatures native to Roshar, and serve a function akin to oxen. They are used to pull wagons or carry heavy burdens.
Chulls, and other similar beasts, are farmed and harvested for their gemhearts - in brief, each such animal has a gemstone growing inside it. This gemheart can be cut into smaller gemstones, to be used by Soulcasters to create food or other commodities.
In the mod, killing a chull will drop one gemheart. This can be taken to a stonecutter to craft the corresponding gemstone.