The Fair Folk, the Kindly Ones, the Robin Goodfellows and Pucks often get short shrift in AD&D. There are few representations of the capricious and dangerous faerie for us to use. One of the primary engines behind this lack is the designation of elves as a player race. Elves are the primary folkloric inhabitants of this space: almost-men who dwell in Annwn or some equally removed-but-present otherworld where they may dance with you until you die, or keep you away from your home for a thousand years and return you to a land vastly changed from the one you recall. But the elves of D&D are a different breed. They're closer to Tolkien, who's elves were themselves already one step removed from the dangerous faerie folk. D&D elves are even farther down the road towards "regular everyday people" of a different branch than that. They retain some of their mystery due to their alienness (and in the 10th Age, the xenophobic tribes of wood elves willing to protect the lives of trees, with whom they often have long conversations, at the expense of nearly any intruder or trespasser) but they are far from the terrifying figures of legend.
What do we have in our Monster Manuals that can return the Fair Folk to their rightful place? 4th Edition tried to do this by incorporating an Annwn into the basic cosmology of their worlds (the Faewild or somesuch vomitous sounding garbage) and making Formori and gnomes into the archetypical Goodly Ones. For us, though, the trick is to pick on the other incarnations of Celtic myth that are left behind: pixies, atomies, sprites, griggs, the D&D leprechaun, etc. In the 10th Age I've done this by making these creatures strongly inimical or at the very least uncaringly capricious. Pixies in particular have had a massive overhaul, transforming them into barrow-dwelling death spirits who wear armor carved from bone and cavort amongst men with the intention of racking up stories to tell to enrich their legendary names back home. These death-spirits are highly feared tricksters who can range from CE to CG and many of whom dwell firmly in the CN(E) category.
The notion of the Fair Folk is one that has powerful cultural anchors, even if they are not squarely medieval. Anything that has cultural resonance extending back into the middle ages is a good candidate for inclusion in a D&D game (save the overriding monotheistic belief system, which sort of squashes the neopagan revival of D&D's many warring gods), so I've done my best to rehabilitate this trope into the 10th Age. It shouldn't be, after all, all that hard to do considering most of the fairy-tale creatures that belong to Annwn can appear human (like the legendary elves) and have a bevy more inbuilt powers (like the legendary inhabitants also did). It merely serves for us to subtly tweak their behavior and cultures so they are less like the cobbler's elves of happy-go-lucky legend and more like the dangerous spirits from which they sprang.