Jaqon

Jaqon was a greater devil and former duke who lived on Avernus, the first hell of Baator, where he was exiled by Asmodeus for a great betrayal. Asmodeus changed Jaqon's name to Dagon, so that if someone tried to summon him, they would instead summon the powerful demon lord's aspect.

Activities
Jaqon led his followers in a battle against Asmodeus, becoming an archdevil in the process.