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)

In 2084, Icthar 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)