The Four Horsemen - The Four Horsemen, #1

The city of New Haven holds one of the biggest warlock populations in the world, blending in with the average people or hiding in secret places. Individuals with powers, or insight, into the magical underworld the Four Horsemen created. For their safety, warlocks try to stay hidden, hunted by a secret army known as the Saints, who seek their destruction at every turn and the fanatical group just gained a deadly asset; a warlock traitor. Jack Devlin, a monster hunter for hire, must track the traitor down with the help of three other hunters.
Even the greatest lone hunter needs help for this job, but can he find and stop the traitor before too much damage is done?