Blood Challenge is book seven in the World of the Lupi series. Try to read the books and short stories in order. It will be worth it.
In this story, she who can't be named is back and still trying to destroy the Lupi. This time she's working through interesting intermediaries, some human and some not. Lily and Rule are both in harms way, but so are all of the good guys. There's a new heroine who plays a pivotal role in this story, and she could be around for quite a while. This series just keeps getting better. Very highly recommended.