Dagon's last ref was made 10 years ago so I think he was due for a new one.
He made a pact with the Demon Lord so he can use Rot Sorcery which is about what you'd imagine it is. It affects his right arm; the more powerful spells he uses the more his arm wastes away and it can spread to the rest of his body if he isn't careful. It heals over time however.
Dagon is from Zenark; part of a trifecta of world's that are interlinked.
A few notes on that:
Zenark is a planet created from Hollace's hell which was a like end of days event for hell and the demons and spirits that escaped went into Interlude; a world of spirits.
Zenark is now a planet full of animal people that are all descendants of demons but they have no idea they are.
Hollace is a modern day Mortal realm where humans and monsters live together. They generally don't know that Zenark exists.
People in Zenark since they're descendants of demons sometimes have the power of visions awaken in them and they can see what's happening in Hollace.
Peyton is in Interlude Chilo is from Hollace and Dagon lives in Zenark.
Zenark is like kinda late Victorian era ish technology
Interlude is magic infused sci fi shit and Hollace has Goatmen and Centaurs using Smartphones.