Sword of Avalon

Yes, that Arthur.

Laurence's soul is bound to a dead warlock's, his familiar is traumatised, and Quentin's baby brother might be a witchfinder. So when a mysterious raven arrives and fails to deliver its message, Laurence figures it's best to track down whoever sent it before his life can get any worse.

His working theory is that it must be Morgan. He owes her a favor, after all, but to reach her he must travel to Avalon, and that turns out to be the easy part, because her brother Arthur has woken up after several centuries of slumber.

And he needs Laurence's help...