Dark Vessel by Julie L. Kramer
Kendra Laws hadn't practiced her craft in years. Not since her sister died at her altar, leaving only one enigmatic clue. But when witches start disappearing all over the city, everyone is panicked and seeking safety under the promises of a powerful new coven, the Black Stars. It seems the only way to survive and avoid the creepy coven is to call on her magic. And her ex. James Becker is right where she left him. In his underground bunker, conjuring and prepping for this very day. After all, he warned her something was coming, warned her she'd need her magic and him, but she'd chalked it up to his paranoid conspiracy theories. And it kills her to admit he may have been right. Now she's at his door, waiting for I-told-you-so's, but he greets her with a passionate kiss and the news that he's found not only her sister's killer, but the person behind a massive conspiracy that starts with the Black Stars and intends to end with a mass ritual death and the purifying of the final vessel...her.
Book Length: Novella - 60-150 Pages