After a Cyber-Scout discovered the Fifth Doctor and the Master, the Cyber-Leader and his squad fired at them and attempted to capture them. However, before they could capture them, the Doctor escaped using the Master's homing beacon. The Master then tricked the Cybermen into working with him to destroy the Time Lords.
When they reached the Dark Tower, they discovered a giant chessboard. When the Cybermen attempted to cross, they were all electrocuted. The Cyber-Leader then asked why the Master had betrayed them, but he told the leader the safe path changed with every journey. After showing the Cyber-Leader the safe path under threat of death, the Master killed him using a Cyber-gun. (TV: The Five Doctors)