Asmodeus is a villain from Dungeons & Dragons, he rules over the Nine Hells of Baator and is considered the grand ruler of Lawful Evil beings. His inspiration is Satan from Christianity.
Although accounts of Asmodeus' past vary, there are many facts that are held by all. During the Creation War, a greater force sent Asmodeus to lead a host of angels against the evil hordes of the Abyss. After the war was over, most of the angels had become demonic in nature. Asmodeus stood as the ruler of fallen angels and remaining devils alike.
Some time after this Asmodeus became involved with the politics of the gods, inventing punishment in order to enforce their laws, in return the gods gave him Baator, an abandoned hell with seven planes. Asmodeus built two more levels onto the plane of Baator, and transformed it into a place of eternal damnation for evil souls. Once he controlled evil souls, Asmodeus set forth corrupting as many as he could, in order to increase his own power.
Asmodeus is known for being charismatic, handsome, and incredibly intelligent, he is known for creating schemes that would not come to fruition for centuries, if not millennia. Asmodeus is also a very powerful warrior (in an early D&D manual it was stated he was the physically strongest of all devils). He is also a powerful magic user, made even more powerful by his use of the Ruby Rod of Asmodeus, which gives him nearly infinite magical power.
It has been said that Asmodeus' true form is a great serpent large enough to wrap itself around Baator, but most of the time Asmodeus takes the form of a 13' demonic human. His humanoid form is notably handsome, and usually decked out in ornate jewelry and regal robes.