Necroquartz

A black glass-like rock that emanates a feeling of dread.

The necroquartz is a naturally occurring mineral from the plane of Mabar. Whenever a creature dies within 15ft, the necroquartz may absorb the extinguishing life essence (before Death Saving Throws are made) Affected creatures must make a Charisma Saving Throw against DC 15.

• When a soul is absorbed, they may not be resurrected until a Remove Curse is first cast on the necroquartz to unbind it. 
• Necroquartz with a recently absorbed soul may infest nearby rock with a one time 1-in-12 chance (1d12) turning that other rock into necroquartz.
• Necromantic spells cast with necroquartz as a component benefit from +1 spell effect and +1 DC spell power.

The hardness of necroquartz is 6. (At least six damage must be made to shape or break the substance)