I'd have Markessa all-growed-up and having created her own servant races in some out of the way place she took over (the Mage of the Valley never impressed me, maybe she kicked his butt and took his stuff?), plus a frustrating amount of personal 'false Markessa's' that the PCs keep thinking are her, only to find out they killed another of her Simulacra.
Greyhawk online has her as a High Elf female Wiz 13 / Hexblade 6, but I'm not in love with that write-up. If anyone is suited to be a Master Transmogrifists, it's her.
PC 'furries' could be escapees from her brutal condtioning (a combination of spells and intimidation and having the 'tribal leaders' do the work of educatin' the young 'uns into a life of brutal servility on her behalf) and perhaps there could even be an underground railroad of sorts, or even a resistance movement, to try and free her subjects from her capricious rule. She would likely use normal animals, and some low-intelligence and brutish race, like Orcs, as the parent material to create her fusions, so her 'moreaus' would generally be strong, but not so bright (and already inclined towards cultures of cruelty, savagry and sullen obedience).