Before he was Acererak the demilich, architect of the Tomb of Horrors, he was Acererak of the Scarlet Robes, a human wizard in the ancient empire of Bael Turath.

However, his mortal days are little known to modern scholars, who know him as the demilich Acererak, revered by some necromancers as the Devourer. His infamous trap-laden dungeon called the Tomb of Horrors is legendary for its difficulty, but the potential treasure therein is supposed to be great. Some necromancers who revere his aspect as the Devourer have created a settlement near the tomb called Skull City, and they train necromancers at the Bleak Academy. They allow adventurers to pass through the city, considering them offerings to the Devourer.

Image retrieved from http://www.canonfire.com/wiki/index.php?title=Acererak on December 12, 2015.