The word for "wolf" is grohiik, and the closest translation for "nether" (as meaning "from the underworld") might either be tum "down/beneath" if you want to stress the "under" part of "underworld," or simply dinok "death".

So then you could say tum-grohiik, dinok-grohiik, or grohiiksetum "wolf of (the) beneath" or grohiiksedinok "wolf of death".