weird fiction feel, at least to me. Sure, its easy to make fun of the Folio--there are a number of misfires there. Any time you talk about it someone always goes and mentions the flumph, so its got that to live down.
But I think there are a number of creatures that would be at home in the works of Lovecraft, Clark Ashton Smith, or any other weird writer you could think of. All they need is the proper context. Let’s take a look:
algoid: Ok, the picture doesn’t help us here, and I’m not sure what this thing's about really, but the basic concept of a sentient algae colony seems reasonably Lovecraftian. He gave us space fungi, after all.
apparition: like the coffer corpse, the crypt thing, and the revenant, these are exactly the sort of undead that show up in weird tales. Admittedly, though, there’s nothing special about them other than the Russ Nicholson art that really gives them a lurid feel. Still, the raw materials are there for building a weird atmosphere, absolutely.
bullywug: Things you can describe as batrachian tend to be sort of weird (this would apply to the slaad as well--which remind me a bit of Smith's Tsathaggua, anyway). I could definitely see the bullywugs in the Dreamlands, but I guess that’s about it.
crabman: Here’s a case where the picture does not help, but crustacean sentients actually appear in a Robert E. Howard tale (“People of the Black Coast”) though their whole deal is a little more aboleth-like there, appearances aside.
dark creeper: these guys have always reminded me a bit of Howard’s portrayal of the Little People. You could always give them a little of the whispery evillness of the lil' demons in Don't Be Afraid of the Dark. This time, the illustration really helps.
Cryonax: a yeti with tentacles for arms doesn’t seem like Lovecraft, but does seem exactly the sort of thing one of Lovecraft’s lesser disciples would have created.
gibberlings: have a name like something out of a weird tale, but I suspect they’d just be a brief, colorful mention in passing in Dunsany or the like.
Githyanki and Githzerai: with their whole feud thing seem like something that could come out of a more science fantasy weird story, and again, the visuals help.
Kuo-toa: or should I say, Deep Ones?
shadow demon: are not too far removed from the menace of the CAS story “The Double Shadow.”
yellow musk creeper and yellow musk zombies: fairly weird fiction-esque at face. It's got the "yellow" thing going on in the name, too.
And that’s just off a quick flip through. I’m sure there are plenty of others sandwiched between the needle men, and thorks--and of course, flumphs.
1 hour ago