Devils were once Celestials of the First Host. They were seduced and corrupted in their war against evil by the Prime Evils. Led by Asmodeus, one third of the Host rebelled against the Creator Gods in a bid to become their own masters. They lost, and were cast down. They became the Devils, and now reside in the Nine Hells. They remain bound by their laws, but have now become experts at exploiting and subverting it. They seek their revenge against the Gods by seducing their followers. Their numbers have grown with the souls they've bargained for being used to create new devils.
Dukes of the Nine Hells
Asmodeus: Asmodeus the ruler of the Nine Hells, Lord of the Ninth, the Archduke of Devils, and a god in his own right.
Mephistopheles: Lord of the Eigth.
Belial: Lord of the Fourth
Beelzebulb: Lord of the Seventh.
Baphomet: Lord of the Fifth.
Dispater: Lord of the Second.
Iblis: Lord of the Sixth.
Mammon: Lord of the Third.
Sammael: Lord of the First.