Rock troll 1E
Rock trolls possess a particular vulnerability to sunlight, becoming sluggish under direct exposure and eventually becoming fully petrified. As a result, rock trolls chiefly inhabit the Darklands and rarely emerge onto the surface. However, they also lack other trolls' vulnerability to fire, and can regenerate wounds inflicted by flame without complications.
Rock trolls are voracious omnivores, and will consume anything they encounter. They can subsist on rocks and minerals when meat is scarce, and will also devour xorns when they encounter them; rock trolls who consume multiple xorns eventually develop tremorsense. However, xorns will also attempt to consume the gem-studded rock trolls, leading to ferocious clashes when groups of the two creatures encounter each other.