Who Set Fire to an Old Conflict?

S1 E3: Only the chosen warriors known as Vessels of Heroic Blood possess the ability to turn their own blood into weapons known as blood armaments. First Chihiro, then his friend Kotetsu awaken as Vessels of Heroic Blood. And who are these people who keep transforming innocent people into monsters?! The Vessels who awakened one after another throughout the course of a fierce battle are taken to Maldeus Church. Once they arrive, the mysteriuos girl Dux has something to tell them...