Demon Accords, book 13.

Faced with writing college papers, prepping for tests, and teaching testy witches, Declan O'Carroll has enough on his plate. Not to mention the magical withdrawal of leaving his very own magical kingdom behind on Fairie. But when he and his friends are attacked from creatures out of folklore and fable, it seems the Queens of Summer and Winter aren't done with him yet. But if they're so eager to mess with Earth, maybe it's time Earth came to them. After all, he's got some lessons to teach.