Tarpok

Tarpok, along with Scibus, was a Silurian companion of Icthar. According to one account, Icthar was the "sole survivor" of the Silurian Triad. (TV: Warriors of the Deep) According to another account, Tarpok was himself one of the Triad, and Icthar's Science Adviser. (PROSE: The Scales of Injustice)

After the Triad awoke on an Earth dominated by humans, the Third Doctor pleaded with the Triad to seek peace with the human race, but this failed after a C19 operative killed Chukk, the leader of one of the shelters. (PROSE: The Scales of Injustice)

In 2084, Icthar, Scibus and Tarpok attempted to take over Sea Base 4 and start a nuclear war to wipe out humanity, but were defeated by the Fifth Doctor. Tarpok later died from exposure to hexachromite gas. (TV: Warriors of the Deep)