Zargon

Zargon the Returner was an elder evil abomination who hungered to drown the world in its slime.

Activities
He was known to take on selected warlocks as their patron.

History
One legend states that Zargon was the first ruler of the Nine Hells. When Asmodeus first rose from his fall, he obliterated Zargon and his armies with the help of his devilish children. Zargon was defeated but his horn couldn't be destroyed so Asmodeus cast it into the Prime Material plane where it struck in what later became the Raurin desert and was buried deeply. Zargon reformed from his horn years later and struggled for centuries to reach the surface where he terrorized the inhabitants of the city of Cynidicea in the Imaskar Empire. They eventually came to worship him like a god and sacrificed many to appease his hunger.

Asmodeus, yet again, stepped in and put him in stone. The devil then buried his worshipers alive.

Rumors & Legends
Legends indicate that Zargon may have been the first master of the Nine Hells. Other stories say he was a Demon Prince that was thrown out of the Abyss.