Isley is a male Awakened being, formerly known as Number One in the Organizations first generation of warriors. In his transformed state, he resembles a sleek black centaur with his right arm acting as a lance or axe and his left as a bow or shield. He has great skill in firing homing arrows. Isley initiated the Northern campaign to kill Luciela and take over the south, becoming an unrivaled power by destroying the possibility of an alliance between Riful and Luciela against him and Priscilla. To do this, he sacrificed his awakened followers to distract the organization and Riful while he went south to eliminate Luciela. The organization sent 24 claymores to slow down Isleys allies, preparing Alicia for controlled awakening. During the North campaign, Isley found Raki and took him in. Later, when Raki complimented his skills with a sword, Isley agreed to become his teacher and began instructing him in swordsmanship. He saw similarities between Raki and his own youth. Seven years later, after sending the awakened beings to the west and east, it was discovered that Isley had emerged victorious against Luciela, nearly killing both of them in the process. Afterward, he remained quiet for seven years before being hunted by Abyss feeders. In the end, he fell slowly and was eaten away.
Riful personally visited Isley as a one-time chance to slay him only to discover that Priscilla had obliterated him in a split second, making her his general and covering up the story. Isley had set his plans in motion by claiming that only something stronger than Abyss ones could defeat him, quickly destroying any possible chances of being defeated by killing Luciela, one of the three Abyss ones, thus preventing Riful and Luciela from forming an alliance against him.