Clemma

Clemma, real name unknown, is a fictional slave and a minor character featured in comic books published by DC Comics. She made a single appearance in flashback in Justice League America #77 in July, 1993.

Biography
Clemma is the name given to a black slave from the American southwest in the 19th century. She, along with several others, suffered greatly at the abusiveness of a plantation overseer named Jacob Whitney.

Clemma and several other slaves conducted an occult ritual, which produced a mystic artifact known as the Blood Gem. They used the Blood Gem to imprison Jacob Whitney's soul inside of a pocket realm. He eventually evolved into the monstrous figure known as Rott.