Acquire a Black Diamond Heart.
The ground bleeds, <class>. They tear it open, as one would gouge flesh.
These cultists relish their secrecy but the very elementals they use for their misdeeds can betray them. Seek out Obsidian Stoneslaves northeast of here, among the ruined earth we have named the Black Breach.
Shatter their bodies and find for me a perfect heart of black diamond. I will look into this heart. And I will bare its soul.