Okay, so basically, it's Prince Vrannus. He's not the only plausible suspect but he has the most red flags hovering around him.
- The prince is directly responsible for the decision to hunker down in the city despite the fact the city's supplies are apparently scarce enough to drive the hobgoblin populace to banditry.
- He's also responsible for provisions in the city, and it's heavily implied the water in the city's public baths and massages is being used to make everyone extra horny and indulgent.
- He's been taking women on the city's ruling councils and military off duty and adding them to the royal harem, which could just be dismissed as sexism if not for the fact he's assuming the oversight he took from them.
- Vrannus is said to be the one who started and encouraged the fashion trend of leaving your tits hanging out or barely covering your crotch.
- Rather than appear with the rest of his family in part two of the party, he only shows up in part three. If you go looking in the palace's private section, you see him getting his ass fucked by a 'mander slaveboy. Also the family shrine of Tira has recently been jizzed all over.
- Vrannus has also apparently become involved with military strategy, which coincides with a major hole in the army's patrol routes and defences that Cait's father, an aging dadbod cat wizard, exploited to sneak into the palace by total accident.
- Finally, a high priestess of Tira, who is strongly implied to be Tira herself incognito, strongly implies it's him and suggests he agreed to become Master Tollus' agent in the city because he's bitter and resentful that he grew up into a skinny girlyboy like his distant cousins in the north instead of a beefcake like most Southern Minotaurs, and because he was already a lazy, self-indulgent hedonist due to living a life of luxury and priviledge in peacetime without being called upon to actually DO anything AND he's convinced that women only want him for his status and to dip their hands into the royal coffers, all of which would leave him vulnerable to being manipulated into becoming a Quisling by Tollus.
Bottom line, the femboy in the Jessica Rabbit dress is our man.