A coal black chunck of unidentifiable rock that radiates with latent necrotic energies.
While these stones are typically associated with “evil” spell casters and the like, the devices themselves are not inherintly evil. Instead they are commonly used as keys, or foci for other magical devices or rituals and were most prominently used by the “Cult of the Reaper” the last vestiges of which dissapeared nearly 500 years ago. Exactly who or what the Reaper is or was is lost to time, but many believe it to have been some aspect of Orcus, or possibly Vecna. Others say it was a being unto itself, a primordial perhaps, or some other powerful and now forgotten force.