The Fimir are back. Mentioned by name, in canon. They were never 100% written out ala squats but it was stated at one point that the skaven wiped them out. God bless you Matt Ward for bringing them back, in fine form. Not only are they back but they can kill your forces if they stumble too far into the wrong sort of mists.
If you don’t know, the Fimir are strange narrow-headed fat-bottomed swamp creatures like something crossed between Salacious Crumb and a waddling skeksis, tres Brian Froud, with a single yellow eye in their narrow heads and a mace-tipped tail ala an ankylosaurus. They can control mists and have a habit of stealing human females to aid their breeding cycles. Also, their chief habitat is the Wasteland which is the Warhammer equivalent of the Netherlands. So they’re not just awesome unique monsters, they’re also DUTCH.
Hooray for Fimir!
Meanwhile, if you want to run a WFRP LARP, have you considered buying a village?