The chaneque is a bat-like fey that kills other fey, stews their brains in their skulls, then uses the skulls to steal the souls of mortals—mortals which, by the way, the chaneque controls until the soul is recovered.
I’m going to say that again in case anyone missed how cool this is.
The chaneque is a bat-like fey that kills other fey, stews their brains in their skulls, then…you get the idea.
Let me back up. Fey are vaguely defined supernatural spirits. They’re usually described as guardians of nature, but there are plenty of spirits of the farm and the home as well, like brownies and domovoi (see Pathfinder Adventure Path #67: The Snows of Summer). But then there are fey that are older…far older. Who don't just guard nature—they are nature—and the chaneques fit this category. To them, guardian fey and house spirits are weak. Puerile. Sentimental. Nothing more than prey to be hunted, devoured, and used. “They see themselves as dutiful punishers of the fey,” the Bestiary 4 notes, but at best that means they’re following the rules of an extinct old order. At worst it means they’re delusional fratricides.
(Here’s another take: Maybe they're fey corrupted to the service of a jungle deity, like the bat demon/god Camazotz. Alternately, some fey aren't old at all but are in fact recently reincarnated spirits…basically Nature’s version of undead. So while chaneques of legend date back to Aztec times, in Catholic areas they are also seen as the spirits of unbaptized children returned as child-demons. If you use this origin, chaneques are probably children who died unblessed in the wild and who hate both forest spirits and mortals alike for not protecting them.)
Also, the chaneque is mythic! In fact, at CR 1/MR 1 it might be one of the first mythic creatures your PCs encounter, while still being well within the reach of nonmythic parties as well.
I think the GM will probably need to use a little kindness when it comes to the chaneque’s steal soul ability—as it’s written, it looks pretty easy for the chaneque to dominate and kill off a low-level PC almost effortlessly just by giving the right commands and then hiding the soul-skull carefully. So you should provide plenty of opportunities for PCs to recover any lost skulls. Thankfully the duration of the effect is short due to the chaneque’s low Hit Dice, so it would need to have the skull on hand to top off the compulsion (and it also lacks the invisibility of many other fey). Or maybe the signs of where they hide the skulls are obvious to the learned. In stories they prefer to lair in kapok trees, so maybe PCs can find the skull by finding the right tree…
Then again, maybe you just go nuts. If a PC loses his soul, it's his own fault for not being mythic enough…
A chaneque has teamed up with a gang of tooth fairies, raiding from house to house. While the tooth fairies go to work with pliers on the humans, the chaneque brutalizes and slays any domestic and garden fey it finds, then uses their skulls to steal the souls of the town’s wet nurses and maids. (In its mortal life, the chaneque was an infant who died after both its mother’s and the wet nurse’s milk failed.)
Adventurers come across a skull-filled side chamber in a many-tiered pyramid. If they fail to perform the right rituals, several bat-like creatures crawl out from the mural, attack, and then flee. The creatures are chaneques, fey of another age long thought extinct. Returning the things to the mural might spark the adventurers’ mythic ascension.
People are disappearing. Farms are going untended. No one returns from the deep woods. An adventuring party’s career is launched when a battered brownie arrives on their door, pleading for help as if it knows them (which it does, having secretly served on the orchards where they grew up). The town guard arrives just as the brownie expires; taking the small form to be a child’s, they try to arrest the adventurers. The young would-be heroes must escape the guard and find the chaneque who is the source of all this misery.
—Pathfinder Bestiary 4 28