The Harlequin (Book #15 of the Anita Blake series) by Laurell K. Hamilton
The Harlequin has Anita and Jean Claude are in trouble with Vampire Council enforcers. Out of desparation, Anita calls Edward for assistance and he arrives the same day, bringing Olaf and Peter (now 16 yo), who we last saw in Obsidian Butterfly.
The Harlequin are the police/judge/jury for vampire leaders who violate various rules (one example is Malcolm's resistance to the blood oath). It was formed by the Mother of All Darkness, modeled in style on the Commedia dell'arte and by action on the wild hunt. It is a group of very old and powerful vampires who like to manipulate the behaviors and emotions of humans or younger vampires and wereanimals - Jean-Claude, Anita, and Richard come under their line of fire. Under this influence, Richard and Jean-Claude nearly kill each other, and Anita must also be repeatedly resuscitated. Anita keeps her guys alive by feeding on first Rafael (and through him, all the wererats in the city); Belle Morte; and later, all the swanmanes via Donovan. Anita's second triumvirate also comes online, with Nathaniel and Damien.
But if wouldn't be an Anita Blake book if something didn't go wrong, so all kinds of mayham ensues. The Harlequin are not following its own rules, so Jean Claude decides to strike back and it ends up being a free-for-all.
This book has it all: the wereanimals, the vampires, the Mother of All Darkness, the Munin, and of course, the auedur. Anita also comes into a new power, almost to the point she is surpasses Jean Claude in strength.