The story opens in Venice with Septem (賽特), a Frankish knight and covert intelligence operative of mixed descent from Gaul who was the lieutenant to Pepin the Younger. Septem possessed an heirloom bronze vessel with an eastern design, which was in fact the Monster Fusion Vessel. He had heterochromic pupils of blue and brown, garnering discrimination and distrust from his peers and fellow knights over his somewhat Eastern appearance. Miles (麥爾斯) (the reincarnation of Satan whose memories and innate powers had not yet been fully awakened), a knight-commander under the guidance of the cleric Cornelius (康那里士) (the Dread Lord of Hell in disguise), was the polar opposite of his rival Septem, enforcing the Church's will without mercy and question, executing those designated as heretics without hesitation, and had the affection of Lilian (莉蓮), a pure maiden Septem had courted in vain.