Buffy and Spike meets demons who's society is lead by human females

I remember a story I read a while ago where Spike and Buffy meet some time after Chosen. Something happens and they meet demons who have to get together with female humans to reproduce and in order to do so they have to eat their mothers. But their society lead by those same females. In the end Spike, Buffy, and Angel fight Wolfram and Hart. I really can't remember anything else besides that.

Thanks if you can find it!

Yup! That's it. Thank you!