Acqua of the Back is the alias of William Orwell, a tall and powerfully built man with white skin, brown hair, and sharply defined features. He originally worked as a freelance magical mercenary from England, earning renown across European battlefields for his tactical brilliance and for teaching civilians agriculture, medicine, and self-sufficiency in war zones, which earned him the respect of being called a sage. He left England just before being formally knighted, converted to Roman Catholicism, and became a member of the Roman Catholic Church's secret division God's Right Seat, where he holds the position associated with water, the color blue, the moon, and the rear direction. A special saint possessing properties of both the Son of God and the Virgin Mother, he is able to use general magic freely. His bond with the Archangel Gabriel grants him Divine Mother's Mercy, a power that removes his physical limits and the negative side effects of magic, allowing him to channel over two hundred percent of a typical saint's strength. This alignment gives him mastery over water, shaping it into hammers, whips, and torrents, and he is a master of rune magic, using the water rune to enhance his speed and attacks. His signature weapon is the massive great sword Ascalon, over three and a half meters long and weighing more than two hundred kilograms, which contains a hidden secondary blade. Governed by a strict personal code of honor, he despises cowardly tactics, spares noncombatants, and honors valiant foes; this code led him to execute Terra of the Left, a comrade who exploited civilians. His motivations are not rooted in malice or blind faith; he seeks to eliminate what he perceives as the source of chaos, Kamijou Touma's right hand, Imagine Breaker, with a goal reflected in his magic name, Flere210, meaning One Who Changes the Reason for Tears. In the story, he serves as a major antagonist, arriving in Academy City and single-handedly defeating Touma, Itsuwa, and the entire Amakusa Christian Church, forcing Kanzaki Kaori to confront him in the first battle between two saints. His defeat by the Amakusa Church's Saint Destroyer severs his link to Gabriel, stripping his divine enhancements and leaving him as a mere saint. Accepting the consequence, he later returns to England during a civil war to rescue Princess Villian, for whom he has a romantic connection, becoming an unlikely ally to the protagonists and protecting his homeland. He shares a deep mutual respect with England's Knight Leader, with whom he made a pact that the Knight Leader would protect England from within while Acqua operates independently from outside.