D&D has a pretty weak stance on “what it is to be fey” — which it immediately subverts with the elf. It’s reasonable; an elf is a player character race, which means it kind of has to be humanoid typed. I mean, I dunno, maybe it doesn’t have to, have to, but it happens to. Can we do better?
Things that are fey: dryads, sprites, satyrs, hags (well, not night hags), pixies, blink dogs. Things that aren’t fey: centaurs, chimerae, cyclops, kobolds, elves, faerie dragons (which, okay, would be a tossup anyway I suppose), fomorians, harpies, goblins (and bugbears), trolls, treants, winter wolves, merfolk, phase spiders, ettercaps, giant owls or eagles or goats, will-o-wisps, pegasi, perytons, pseudodragons; even the titanic empyrean is a celestial.
That’s not sane, right? What does fey even mean?!
Okay, to start with: per the MM, we know that fey are magical creatures closely tied to the forced of nature. They dwell in twilit groves and misty forests. In some worlds, they are closely tied to the Plane of Faerie (ed: which is pretty self-referential if you think about it). Some are also found in the planes of Arborea and the Beastlands.
I think there’s a few other hidden assumptions; if it showed up in greek myth, I think there’s a sort of slant towards being more fey than not (why else the Satyr, other than the sexual dimorphism thing they have with nymphs, which got specialized to the dryad?). If it showed up in a book by someone named Grimm or Lang, I think there’s a tendency towards the fey also, why else the hag?
Frankly, I think the giants and humanoids that are not fey got that way because D&D stole their names; in what universe does goblin- or troll- being as diminished as they are make sense?
And then there’s the drow and duergar and svirfneblin. They both have to pull dual duty as the PC-race-of-the-underdark and creepy-enemy-inspired-by-myth-and-legend. But they’re kind of funny! Consider first the duergar. They’re medium (but they’re dwarves, so go with it for a sec), they can magically become large or invisible. The invisible isn’t really among the archetypical powers of the creature I’m about to name, but the warlike nature sure is (they’re pretty hefty, waring armor and sporting martial weapons) — they’re basically redcaps. Changing size, the occasional murder. I think I’d make their native size small instead of medium, but that’s literally the only change I’d make. I might even say these are my goblins, always and forever.
Next, the gnome-comma-deep. They have innate castings of blindnessfo/deafness, blur, disguise self; that is, they’re easy to overlook changeling tricksters with resistance to spells, an underground bent towards digging… Slap the fey type on them and they’re knockers! That’s the same mine spirit that gave us kobolds, which definitely has some shades of irony to it, but they work fine as is. I might even say these are my kobolds, now and forever.
The Drow… well, I call them Fomor and just move on with life. Obviously fey. Done.
The Drider then presents a somewhat special case; I like previous editions’ Aranaea, but even without them creepy spell-weaver types (and make no mistake, always use the sidebar!) seem awesome. I think they’re probably just monstrosities and not fey, though. I’ll just use them standalone, same as the in-my-campaign leaderless yochlol.
From that opening harangue, I think I’d promote the faerie dragons, fomorian giants, pegasi, peryton and will-o’-wisps to fey, straightforwardly.
I think underbridge-troll demands a different type of creature than D&D troll. I also think centaur doesn’t fit — but an artemis-y centaur probably would! http://homebrewery.naturalcrit.com/share/Hk1w29lN (I’ll figure out how to embed next time 🙂 ).