Riful (リフル, Rifuru, possibly intended to mean Riffle, corresponding to her awakened form) was the Claymore #1 of the first generation of female Claymores. She was the youngest Claymore to Awaken. She appears to be a whimsical and cheerful young girl but is completely amoral with a disregard for anyone other than her goals. She lives in the Western territory, together with her lover Dauf and wants to create powerful Awakened Claymores by means of torture. This is part of her struggle against Isley, the ruler of the Northern territory.
Jean, Clare, and Galatea got Riful's attention as possible "recruits", but she decided to wait for them to become stronger before turning them into her awakened allies. She also warned them that Isley will not be as gentle as she was when she defeated them (Volume 9). Riful has said that the only way to beat Isley is to join her. In her transformed state she becomes jet-black and can disassemble her body into thin strips. She uses this ability to avoid sword blows or attack her foes.
In the new arc, Riful attempted to recruit Audrey and Rachel, among others. She states that she is looking for claymores who are skilled at sensing and manipulating yoma energy. She needs them for "something interesting" that she found, believing it can even out the balance of power between herself and the Isley-Priscilla alliance.
It was also she who realised that there was something amiss about the story of Isley defeating Priscilla, for she noted that Priscilla was much stronger than Isley, her or Dauf. This was one of the few times where she showed real anger.