You may be looking for Antodus (Dr. Who and the Daleks).
Antodus was a member of the Thal expedition to seek another way into the Dalek City via their water supply system. His brother was Ganatus.

Antodus became distressed after the death of Elyon and was reluctant to continue the mission. However, after a rockfall blocked the way back, Antodus was forced to continue the journey.

Ian Chesterton helped the Thals jump across a chasm in this system to progress by supporting the expedition with a rope tied around him. When it was Antodus' turn to jump, he missed, pulling Ian down. Unable to pull himself back up the smooth rock face, Antodus cut the rope and fell into the chasm, saving Ian's life. (TV: The Daleks)

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