Samilin-Corrath-Gahar was an Andalite, and captain of the Ascalin. He was a traitor, voluntarily working with the Yeerks even though he wasn't a Controller (Ax considered and rejected the idea of him as a Controller on the grounds that it was impractical to assume that he would have been able to keep a Kandrona generator secret on a ship the size of the Ascalin).