Spoiler: Fey Options
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The Ankou is a Large fey (5 ft. reach, sadly) that's got Blindsense, 60 ft. flight (good), a whopping 5 natural attacks (3 with a 2d6 bleed effect), and DR 2/Cold Iron.
The Boggart is small, and doesn't deal notable damage. However, it's got a 10 ft. reach and the Abduct ability. I'm unsure if the Psychic Magic available to it allows for the spell-like ability caveat in Fey Form, but if so, it's got access to Invisiblity.
The Boggle is small, has a climb speed, 4 natural attacks, DR 2/Cold Iron, and spell-like ability access to Invisibility and Dimension Door (unlike other fey options I've seen thusfar, this Dimension Door is not limited to self-only). Constant Greater Magic Fang as well, if you've done some Spell Blending.
The Cold Rider has got Darkvision, a decent natural attack, and icewalking. It's also got a pretty hefty list of weaknesses, though.
The Ekekeh is a Large Aquatic form that's got darkvision, high swim speed, DR 2/Cold Iron, and a rather "ouch-worthy" natural attack that includes electricity damage, on top of the spell-like option for Lightning Bolt. A cursory glance at standard aquatic baddies showed a few results for electricity vulnerability, so I thought that might be worth mentioning.
The Fey Giant Toad is a Large frog that has scent, swim and fly(?) speeds, DR 2/Cold Iron, and a natural attack with grab and 10 ft. reach. It can also Glitterdust as a spell-like. Unsure if its Poison Skin falls under "poison" listed in Fey Form II. I'm guessing not, but there it is.
The Fey Wolverine has darkvision, scent, burrow and climb speeds, and 3 natural attacks.
The Glaistig has... A lot of stuff that I'm not sure what to make of. It's CR 21 and Mythic 10 -- I'm not really sure how many, if any, of its attacks would translate into Fey Form. If any of them do, however, it would be rather stupidly powerful.
The Grig seems great for stealth and scouting. Tiny, decent flight, ability to cast invisibility on itself.
The Grimm is Large, has 10 ft. reach, and a trio of very painful natural attacks (2 claws for 2d8 each). Notably, it does not benefit from the usual DR, as it's against silver/good.
The Grimstalker is medium, has a climb speed, and has a couple natural attacks, but both apply Dex poison that requires multiple saves to cleanse.
The Huldra has darkvision, scent, and two natural attacks -- one of which, interestingly, does Charisma damage. It's listed under the attack, but also as a special ability, so I'm not sure if it applies.
The Ijiraq is a solid natural attacker that can, finally, be used with Fey Form I, as it's medium. 4 natural attacks (a pair of 2d4s and 2d6s, each), and the ability to use Fly, Dimension Door, and Sleet Storm as spell-likes. No speed or senses worth writing home about, though.
The Kamaitachi is medium, has scent, a fly speed, and 4 natural attacks -- All of which have a 19-20 crit range for x3 damage, in addition to applying bleed. Ouch. (This might be a candidate for Pouncing Fury -- all four of those are claw attacks)
The Lurker in Light is largely unremarkable, save for its poison, which has STR drain going for it, on top of STR damage.
The Nereid has a poison that can target touch AC, at melee or range. It's got a high save DC, and inflicts Con damage and blindness.
The Oceanid is an aquatic that has a high swim speed, darkvision, tremorsense (in water), and a particularly damaging ranged natural attack (7d6).
The Pooka is unremarkable beyond its poison, which damages both WIS and CHA at the same time. Or, it can make its target drunk.
The Remacera is Large, has reach, and has a bite attack that does decent damage -- including sonic damage.
The Rusalka is Medium, has 4 painful natural attacks that each have 15 ft. reach and come with grab, and the constrict ability.
The Sangoi is Small, has 3 natural attacks that all come with bleed, and Blood Rage.
The Stroke Lad has a natural attack that comes with 1d6 DEX drain.
The Vilderavn is medium, has See in Darkness, high land and fly speeds, and some solid natural attacks -- all of which have bleed, and the bite attack has a crit range of 15-20.
The Whisperer is Large and normally CR 20 -- See in Darkness, top-notch flight, and 6 natural attacks that hit for 3d10 each, against touch AC, with a 19-20 crit range.
The Wild Hunt Horse is Large, has reach, high speed and 3 natural attacks, two of which have bleed. Can possibly be ridden, for maximum ridiculousness?
The Wild Hunt Hound is medium, comes with almost every sense you'd ever need (scent, blindsense, see in darkness), has a decent speed, and three natural attacks. The bite attack trips.