Yuriel is a silver haired whip user who is part of the Aincrad Liberation Force. She is devoted to aiding Thinker with his duties. She seeks the aid of Asuna and Kirito after she heard that two strong players from higher floors had come to the first floor. Thinker had been trapped by Kibaou in a hidden high-level dungeon that had recently opened up below the first floor. After journeying with Kirito and Asuna to the center of the floor, she grabs Thinker and is told by Kirito to escape with a teleport crystal.

(Source: SAO Wiki)