Slayers (1995) : 1x23

Rezo's secret is revealed in the book found in his institute. However it is too early to celebrate as Rezo and Eris storm into the institute. Rezo has great power and Lina discovers that this Rezo is a clone controlled by a device on his forehead. Eris is also very tough. Two fiends take the book of secrets back and in a split second attach the control device on Gourry. While Lina and Amelia are busy holding down Gourry, Rezo and Eris break Rezo's seal and create Zanaffer, a demonic beast. Eris is excited to find Rezo's inheritance. Then, the clone Rezo attacks Eris. When the clone is out of Eris's control, it is awakened to his self-conscious and resists the master.