Zibbine

This bloated, corpulent man has a bald head, a maniacal look in his burning red eyes and a mouth full of pointed and crooked teeth.

Source: Dunes of Desolation (Pathfinder/Frog God Games)

Cool Factor: Eunuchs are known to be entrusted to protect or watch over a man's harem. Being a eunuch helps relieve the temptation of this important duty. In very rare instances during the process of becoming a eunuch things go wrong and a young boy is transformed into a Zibbine. The process is almost instantaneous. Within a few hours of the botched procedure the young boy turns into a full grown adult with corpulent features, yellow eyes, and crooked pointed teeth.

     This monstrous humanoid removes itself from society and lurks in subterranean lairs. There they plot revenge against those who were responsible for their current state and against men who flaunt their romantic escapades. The Zibbine are known to be excellent grapplers and have the ability to neuter their foes.

Combat: The Zibbine is a chaotic evil monstrous humanoid who specializes in unarmed combat and the ability to grapple its enemies. He's a CR 6 creature. The most signature ability of the Zibbine is detailed below.

-Neuter: The most interesting ability of the Zibbine is the ability to neuter its foes. When a Zibbine bites an enemy they must make a fort save or lose it's gender. The effect is temporary and only last 1d4 minutes. However if the creatures saving throw is a natural 1 the effect is permanent. Yep you just lost your manhood(or womanhood). Also the abrupt lost of gender is greatly disturbing and requires a will save. Failure leads to a -2 penalty to attack rolls, weapons damage, and saving throws for the duration of the transformation. The effect of the neuter ability are considered curse based and can be removed with spells that cure those conditions.

Verdict: I don't think I've ever encountered a creature with the ability to neuter a character. The role-playing implications are pretty priceless. Having your brave fighter losing his most prized possession even if only for a few minutes is rather entertaining. The Zibbine provides an interesting monster background that ties in nicely with a entertaining monster ability.