Black Blood Mates

Black blood mates.

Two werewolves that have powers that can be used to create new creatures.
This can be done by feeding the blood to a female of age. Once the blood is in the system a new creature will form inside her. This process can kill the female and can create monsters which can wipe out any living organism.

It has happened before and it wiped all the whole Centaur species and the only way to kill them is to stab them in the heart with a gold weapon.

Halsey and her mate are black blood mates. Her mate has been taken by Hunters who want to create new life by using his blood. Which can spell death for every other creature. They have to be stopped before life on Earth dies out.