Eternal Rider by Larrisa Ione

This is a nice spin-off series from the Demonica series. Lots of old characters pop in. This new set is about the Four Horseman of the Apocalypse.  This first book is about Ares, who would become War. His brother Reseph's Seal has broken and he is now Pestilence. Pestilence is trying to murder the person who holds the key to Ares' Seal, so that Ares will become War, the apocalypse happens, and evil reigns.  I really enjoyed this book. And Hal, the hellhound, is cute, lol.