Can you help me find this?

Hi people!
I'm trying to at least trying to redo my "already read" list (which has few titles compared to others) but I can't find one title no matter what...

It was straight smut with an archmage betraying his party bc the boy hero, the girl paladin and the saintess mistreated him. The archmage was called something like "Pastrache"(?) and he joined hands with the evil lord (or demon king) who's an old guy who give him an innocent succubus as his sidekick