Toberman

Toberman was Kaftan's servant. He accompanied her on Professor Parry's expedition to Telos.

The expeditionary party blasted through rock face of a cliff and found the entrance to the tomb of the Cybermen. After the door had been de-electrified, it was found to be too heavy to move.

Kaftan was unwilling to have Toberman open did not want him to lose his life. Parry suggested they had only brought him along for purposes such as these. The Second Doctor was able to play on Toberman's pride to have him open it, accusing him of being afraid. He complied, granting them access.

Kaftan wanted Toberman to stay with her while Parry, Eric Klieg, the Doctor and other members of the party went down. However, the Doctor was unwilling to leave him behind, so Kaftan instructed him to go too.

After Klieg woke the Cybermen, Toberman was taken prisoner along with the others. However, while Hopper rescued the rest of the group, Toberman was separated and recaptured. He was partially cyberconverted, with his right arm replaced with that of a Cyberman and his mind bent to the will of the Cyber-Controller.

Together, Toberman and the Cyber-Controller went to the upper level. The controller agreed to release Toberman, with the Doctor and Jamie McCrimmon observing the change in his disposition. Under the Cyber-Controller's instructions he attacked Klieg, knocking him unconscious. However, when the controller killed Kaftan, the Doctor was able to successfully appeal to his humanity and he turned on that Cyber-Controller, lifting him above his head and throwing him into a control panel.

Toberman then accompanied the Doctor back into the tomb, acting on the Doctor's instilled value in him to destroy evil. There, he was able to wrestle with a Cyberman while the Doctor restored the others to their dormant state. He damaged the panel on the front of its casing, killing it.

The Doctor prepared an electrical current that would seal the entire tomb. However, the Cyber-Controller revived and moved to attack them.

Fleeing back outside, they attempted to close the doors which were the final piece in the electrical flow, but were unable to battle against the strength of the controller. In full knowledge of the consequences, Toberman stepped up and forced the doors together, sealing the tomb. The circuit complete, Toberman and the controller were both killed by electrocution. (TV: The Tomb of the Cybermen)

Behind the scenes
Toberman was intended to be deaf, but there's no reference to this in the episode. However, it did make it into the novelisation.