Mephistopheles, self proclaimed the Prince of Darkness, was a demon from Hell. He made a deal with the dying actor Jasper Murdock for his life, but when Jasper proved himself to be pure of heart, he was released from the deal.
Other characters had also used the name, like Doctor Mephistopheles, Satan, the Mephistopheles of Murder, and Brimstone, the modern Mephistopheles. Mephistopheles was adapted from the German demon of the same name by Jack Kirby, first appearing in Tales of the Unexpected #13 (1957).
Prime Earth
Justice League Dark
Amalgam Universe
Satanus/Mephisto
Earth-Two
Radio Squad villain
