From publisher blurb:
Welcome to Faeries of the Fringe, the tenth in our Monster Menagerie line of monster books. Each volume in this line presents a small set of monsters tied to a single theme, but spread over a range of CRs. For Faeries of the Fringe that theme is fey folk who dwell off the mainstream (and are often tied to niche environments the way more common fey are tied to trees and forests). As an added bonus, author Sam Hing has put together an awesome set of fey-related magic items, spells, and feats to round out your wicked wise women.
While fey are classically considered to be most dryads and fauns, perhaps knights of some otherworldly Fairy Court, there are many cases of spirits tied to specific locations or ideas from mythology that could be considered to be “fey” in rules terms. This product looks at both some examples of such creatures in mythology and some niches common to fantasy roleplaying game campaigns, and posits what kinds of faeries would be attached to them. The end result is a whole new set of foes ranging in power from CR 2 (the glade maiden) to CR 10 (the river mother), ready to force the PCs to fight, flee, or negotiate.
So stay out of the fairy-rings, put some milk out on the sill, and keep your cold iron handy. The charnel-kin are stirring, the nightswans are counting their tribute, and the river mothers are always on the lookout for new husbands.