The acronym for the "huge, world-wide crime-organization" headquartered in Sinsubhani. The name D.E.M.O.N. "stands for its aims --Destruction, Extortion, Murder, and Overthrow of Nations" (S No. 191, Nov 1966: "The Prisoner of DEMON"). The blind agents of D.E.M.O.N. are led by the nefarious Dr. Demo.
In November 1966, Superman is given a mysterious alien gem known as the Sacred Star by the Maharajah of Sinsubhani. The gem, "formed in the heart of a real star at the center of the universe...and spewed forth when that star exploded," is imbued with a destructive power that threatens Earth. When the Maharajah is assassinated, Superman swears to avenge him, vowing, "I will wear this gem until I have the means to destroy it...and DEMON as well!" After failing to defeat Superman, agents of D.E.M.O.N. kidnap Jimmy Olsen and Lois Lane, forcing Superman to hand over the gem to Dr. Demo who in turn destroys it using a special device and reveals himself to be the benevolent Prince Krishna, son of the Maharajah (S No. 191: "The Prisoner of DEMON").