Rites of Passage by A.D. Starrling

It’s all fun and games until someone pisses off a Witch Queen…
Weeks following the events that led to her awakening and her initiation into the New York coven as the Witch Queen prophesized to rule the world of magic, Mae Jin is still trying to get a semblance of her life back together. But disaster strikes when her apartment gets attacked by ghouls, driving her into the thick of the action as she helps Nikolai Stanisic figure out the origins and purpose of a mysterious skeleton key that falls into his hands by accident. A key the Dark Council was guarding.
Forced to travel to Philadelphia for the Annual Grand Meeting of all covens, Mae finds herself treading a fine line amidst the cutthroat politics of the covenstead and the senior witches and sorcerers who wish to put a leash on her. When they discover that local magic users have gone missing, Mae, Nikolai, Vlad, and the others stumble upon a link between the disappearances and the skeleton key.
After Nikolai’s brother Oscar and the demon Barquiel steal a sacred grimoire from the covenstead, Mae realizes all the incidents are connected and that there is a traitor amongst them. With help from some unlikely allies, Mae and her friends rush headlong into a race to uncover the secret behind the skeleton key and the book of spells. Will they figure out the Dark Council’s wicked scheme before all is lost?
Nerves will be frayed. Steak will get eaten. Snark will be committed.