This is one of those "everyone needed to be a lot more careful with their words" things (because it's one of those frankenstein stitches I mentioned earlier where two games on a very similar system were not designed to be plugged together).
Fomorians are the Elder Darks, the gods of nightmares. They wouldn't be a in a building, they don't exist in the physical world, they're trapped in the deepest Dreaming.
The Fomori are possessed humans corrupted by servants of the Wyrm, the celestial incarnation of entropy and destruction run wild. Black Spiral Dancers are werewolves pledged to the Wyrm who are commonly accompanied by Fomori. (Any other werewolves would drop everything to kill Black Spiral Dancers, they're pretty much the worst thing that's not a Vampire as far as the Garou are concerned)
The two are not related in any way.