Hunter’s Descent by Lise MacTague

While investigating the deaths of multiple students at a boot-camp style institution, Malice and Ruri become trapped in the mysterious Kingdom of Flower and Bone-a netherworld filled with both magical and malignant beings. But which is which? Even ancient forces aren't immune to petty squabbles. Will the pair make it out alive? Mary Alice Nolan, code-named 'Malice,' is a Hunter: genetically modified and rigorously trained to track and kill supranormals ('supras') such as werewolves, vampires, and demons. Seeking revenge after her sister is malevolently 'turned' into a werewolf, the last thing the hot-tempered Malice expected was to develop deep desires for one of her sworn enemies. Ruri Samson is a magnificent golden-eyed wolven without a pack. Smart, sensitive and loyal, she considers Malice her mate. Ruri would sacrifice her own life to protect her--and this time she just may have to. Hunter's Descent is the sequel to Five Moons Rising.