Mysterious monsters without much explanation?

[KageTokage]

For that matter, has the ambystoma made any sneaky appearances post 6.0?

The shoebill seemed to have at least one cameo per patch up through 5.3, but I haven't noticed the former since Ultima Thule.

And another thing to remember is the fae were also shown to have existed back pre-Sundering, and presumed to be an Ancient creation too - a certain sidequest in Elpis shows a fairy (an Il Mheg fairy, not a SCH fairy which is not the same), under study, with the puzzled Elpis researcher assigned to study it at a complete loss to explain it or knowing who even who created it in the first place. And their puzzlement turns to utter bewilderement when said fairy soon turns into a beaver, causing the fed-up researcher to throw in the towel and tell the WoL "Now let us never speak of this again". So the mystery remained! (Presumedly the Ancient researcher quickly swept the records of it under the rug).

The faefolk were always a...weird case to me given that they seem to be wholly absent from the Source.

They're believed to be the souls of children who somehow didn't pass on to the Lifestream and instead lingered in a new shape, but that's a strange exception to the usual permanence of death given that even ghosts are hand-waved as not literally being souls of the deceased but rather more akin to arcane constructs created by the lingering sentiments of those who've already passed on proper.