The Sandrian Chronicles: Written in Blood

Fate has forced Trey Thomas and Adalius, two natural enemies, into an uneasy alliance against an evil more powerful than either have ever faced. Only together, the slayer and the Sandrian vampire can stand a chance of defeating Anna; if they don't destroy each other first. As the unlikely pair pursues their common enemy, the apprehensive Lycan watch as a confrontation looms on the horizon: a civil war between New Bloods and Old Guard vampires which threatens to trigger an all-out supernatural conflict and could spell the end of them all.