When Felix Chambers's Master, a retired paladin who goes by Rose, disappears under unclear circumstances, she leaves nothing but a vague note. Felix, a half-demon whose residence with Master Rose had been kept mostly secret, must rely on two recently made friends for help: a grouchy orphaned rogue, and a bubbly pink-haired eight year-old seeress. When they are taken in by an organization dedicated to slaying demons, more questions are raised than are answered. Who is the strange man with horns Felix was confronted by? Where was Master Rose? What was this vision more and more seers kept seeing, a vision that implied Felix decided the outcome of an entire war? This wasn't just any war, either. The strange man with horns leads an army of demons on one side, creatures from the lower world of Aksen. The humans and archons are on the other side, from the worlds of Neska and Endivask respectively. As if this weren't enough, being the decisive factor of a Massive war was just one of Felix's troubles. After binding his soul to a demon in an attempt to protect someone he loved, he became half-demon and obtained a dangerous, unstable alter-ego--Void. His volatile presence keeps the demon slayers at the organization nervous and on edge. It's only a matter of time before he kills someone--or worse--and Felix has no choice but to be brought to the attention of the law. It's only a matter of time before he's exposed to a world he's not ready for.