The Cyber-Controller gave orders to the Cyber-Leaders and their subordinates from a central base.
On Telos, the Cyber-Controller awoke with the other Cybermen from the Cyber-tombs and took charge. Taller than the others, the Controller had an enlarged, dome-shaped semi-transparent brain case lit from the inside. He also lacked the Cyberman chest unit. The Cyber-Controller had such authority that, upon awakening, the other Cybermen appeared to salute him. (DW: The Tomb of the Cybermen)
Later, he served to co-ordinate from Telos. He recognised The Doctor, who he had met previously. The Controller had changed physically, now having changed to resemble the other Cybermen of that era. He had a chest unit. He now had a metal, though still enlarged, brain case. (DW: The Tomb of the Cybermen)In NA Iceberg The Controller is seen as he was before the Second Doctor met him on Telos revealed to be the Cyber-Planner with a cyber-converted body (which explains the large cranium).
Notes
- It isn't completely clear whether or not there is more than one Cyber-Controller, but consensus seems to be that there is only one.