A Writer's Bookshelf: The Dictionary of Demons by Michelle Belanger
Okay, now bare with me here and don't panic. This is NOT a book that every writer needs on their bookshelf, but, in terms of great names and sources of evil intent, as a way to amp up the bad-ass-ness of your characters (villains), then this is a good reference. And, hey, if you're writing about angels and demons, kinda relevant too! If nothing else, this is a fun book resource that you're going to look at and go: "what was I thinking when I bought this?" and hide under your bed where it doesn't haunt your nightmares, but it's a good resource for those dark writings.