Tony S. Daniel 
Edenwood #4 [PDF ebook] 

Flashbacks reveal that young Rion and his Demon Killer mentor, Bastille, are closing in on the Black Lake Trio, who Bastille has been hunting throughout the Edenwood. Current-day Rion and his new allies discover a gang of demons who are responsible for the purge of the last surviving Demon Killers. Rion must decide to stay and fight demons in the Open Lands or return to Edenwood, where he faces almost certain death at the hands of the Demon Kings and their army. A TRAITOR is discovered within the Witch War Council.