Xerxes wakes up to find himself transformed* after an innocent love bite on his neck during their threesome...! In this, a subtle ability is revealed - those monsters who were summoned (unlike those in Men+Monsters who were born as they are) with the sorcerer's magic can turn others into creature people, with undesirable forms and strange abilities...
*where his head is severed, it's going to look like Osric's fire / magma, because 1. it's a little thing that ties them thematically since he's the one who turned him and 2. I'm trying to keep this from becoming gory haha :>