The Medium by MR Graham
Series: The Books of Lost Knowledge, Book 3 · Liminality, Book 1.
Approx. 103,610 words.
Published on December 1, 2013.
Lenny is good at being a medium, helping spirits pass beyond the Veil, but as a vampire incapable of violence, he has always been a bit of a joke.
All it takes is a stumble into the wrong place at the wrong time to run him afoul of Sebastian Duran, a lunatic who controls other minds better than his own. With a wizard's help, he may escape his own potential for monstrosity, or he may succumb.