Icthar

Icthar was the sole survivor of the Silurian Triad.

Following his revival into a world dominated by humans, Icthar decided, with his companions Scibus and Tarpok, to take over Sea Base 4 with Sea Devil troops and a Myrka, and trigger a nuclear war between two human factions. The Doctor had met Icthar before this incursion, having tried to mediate between the Silurians and humanity. The Fifth Doctor believed him to be killed, but he had not. After recovering from hexachromite gas poisoning, Icthar shot and killed Commander Vorshak with a Sea Devil weapon. Turlough then forced the weapon from Icthar, and killed him with it. (TV: Warriors of the Deep)

Behind the scenes

 * Some fans  commonly associate Icthar with the surviving member of the three Silurian leaders, "Silurian Scientist", seen in Doctor Who and the Silurians.
 * The Target novelisation, Doctor Who and the Cave-Monsters, gives alternative names of all three and does not list Ichtar as one of the three.
 * Additionally, Icthar appears in the novel The Scales of Injustice, which also establishes that Silurians belong to different races or sub-species, with Icthar belonging to a different sub-species than the one seen in Doctor Who and the Silurians.