A Cyber-Controller, identified as the CyberTelosian Controller by ArcHivist Hegelia, (AUDIO: The Cyber Nomads) directed the rest of his race, via the deputisation of less powerful Cyber-Leaders, as their ultimate mastermind. First seen in control of the Telosian forces in the Cyber-Tombs, he later relocated to Cyber-Control.
In the 25th century, the Second Doctor and his companions found the Cyber-Controller in the Cyber-Tombs, and he immediately took charge of the Cybermen. He told the archaeological party they would become the first of a new race of Cybermen.
Toberman, a partially cyber-converted human attacked the Controller after he killed Kaftan after she had fired on him with her gun, just before the Doctor sealed off the Cyber-Tombs, freezing the Cybermen once more. (TV: The Tomb of the Cybermen)
Unbeknownst to the Doctor, the Controller survived. On returning to Telos, the Sixth Doctor met the Cyber-Controller again, this time in a more advanced body. He interrogated Lytton and prepped him up for conversion. He tried to kill the Doctor, but Lytton stabbed him in the arm, causing him to bleed green fluid. The Cyber-Leader and Lieutenant attempted to assist him, but a blast from a cyber-gun fired by the Doctor killed them. The Cyber-Controller waved his arms frantically trying to kill the Doctor, but in self-defense, he fired the cyber-gun again, seemingly destroying the big-domed leader for good. (TV: Attack of the Cybermen)
However, one account noted that as the Second Doctor had been equally certain the Cyber-Controller was dead the first time around, it was very much possible that the Sixth Doctor had been mistaken — (PROSE: The Powers Behind the Throne) as evidenced by the fact that the Cybermen continued enacting complex schemes at later points in their history, suggesting they still possessed their Controller. (TV: Silver Nemesis, PROSE: The Powers Behind the Throne)
Taller than the others, the Controller found in the Cyber-tombs on Telos had an enlarged, dome-shaped semi-transparent brain case lit from the inside. He also lacked the Cyberman chest unit and the Cyberman head handles, and his head was grey instead of silver. The Cyber-Controller had such authority that, upon awakening, the other Cybermen appeared to salute him. (TV: The Tomb of the Cybermen) Later, when he co-ordinated actions from Telos, the Controller had changed physically, now having changed to resemble the other Cybermen of that era. He had a chest unit, but still lacked the Cyberman head handles. He also now had a metal, though still enlarged, brain case. (TV: Attack of the Cybermen)