Blackrat
He Who Lurks Beyond The Veil
I nned a name or type of a female spirit... I'm thinking like a nymph but not a nymph.
Then if you wish to move away from greek words how about: Rusalka
Okay, now let me know if any of these have helped you at all. I can think of several more if you need. Just let me know what kind of word you wish for.