the Jester
Legend
The foulspawn feel distinctly "4th ed" to me. You can practically see the combat roles and encounter design dripping off them. Also, the name doesn't evoke "far realm" to me - it sounds Abyssal.
I suppose that's not really a problem, but that's my reaction.
They actually first reared their creepy heads in 3.5; I think they were in- maybe Lords of Madness?
Yes, the Gibberish mouther and some Foulspawn as described sound more Moorcock Chaos than Lovecraft Horror.
Agreed, but I like the Far Realms as being a bit of both.
I really would like to see a 5e uvuudaum.