SexLab the Mask: It's an idea I've had for a long time. The player equips a cursed mask that alters their behavior. The mask randomly equips itself and chooses a random skimpy outfit for the player to wear.
There will be dialogue that leads to sex with an NPC, and maybe AOE spells that cause sex with enemies and temporarily enthrall them.
Bimbo disease: Similar to porphyric hemophilia. It is a multistage disease that essentially turns the player into a sex addict. In the early stages, the disease is curable. It may cause increased arousal and random masturbation. As the disease progresses, it causes body changes that make it impossible to equip armor. The player may need to visit a seamstress or blacksmith to have custom clothing and armor made.
In the later stages, the player will become dumb. They can easily be fooled by NPCs who claim they will help cure the disease, but who are only there to take advantage of the situation or make it worse.