Claymore number two of the 77th generation before Priscilla claimed her spot. She is known as "Quick Sword Irene," capable of lashing out innumerable lightning fast sword strikes by accumulating all her Youki energy into her sword arm.

Even though she was considered dead by the Organization, she merely lost an arm from the encounter with the Awakaned Priscilla. She saves Clare from Ophelia and teaches her the Quick Sword technique. Irene gives Clare her right arm, so that she can control her technique better. After Clare leaves her shelter, Rafaela appears and presumably kills Irene.
In the final chapter, it is confirmed that she, in fact, survived and regenerated both her arms.