Abraxas is a demonic lord who had made deals with the heroes in the past. Nigel later made a deal with him to gain more power, and Ping bargained for the life of Bartleby.
Using the heroes as pawns, Abraxas managed take Gloomwrought from Bezos and install his own pawns to rule.
Abraxas' powers have been compromised since a mortal cut the demon lord off from the demiplane on which he stores his collections. Rowan took advantage of this weakness, stealing all the wealth from his pawns on the plane of shadow and installing less awful rulers.
This demon lord has since rebounded, and now holds the entire soul of Ping the Vile following a bargain to destroy Bezos and save The Questors.