The Ghost Within. The Bloodseeker Series, #3

The day Opal observes her boyfriend locking lips with a gorgeous blonde is the day her life goes to pot. People turn to ash before her eyes, then her parents move the family into a creepy house left to them in a will by her great uncle. In the house, objects start disappearing and a a sleek black creature saves her from a bolt of lightning meant to kill her. She feels her mind is sinking into insanity, except everything seems so real and more absurd than the vampire shows she watches.
She surmises her imagination must be defective. Meanwhile Nova -- the sorceress -- keeper of night magic and the mother of Bloodseekers, is sinking Earth into a thick cloud-covered darkness, each day colder than the next, and the Slayers still haven't found Agate the empath. Without her they can't destroy every Bloodseeker on Earth or stop the inky blackness from taking over and feeding Nova's night magic until the light is gone forever. Even the unique witches they have ties with can't stop her without the seventh Slayer.
Can the Slayers reunite all supernaturals and find Agate to defeat the dark forces and save humanity?