Planet of the Dead
Sorvin was a Tritovore who came to San Helios to trade.
His colleague, Praygat, and he were marooned on the barren planet when their ship’s drive system cut out. they used surveillance cameras to observe the planet until they saw the arrival of the 200 bus. they brought the Tenth Doctor and his companion, Christina de Souza, back to their ship, thinking they were behind the destruction of San Helios. However the Doctor proved them wrong and offered to help them. The Doctor and Christina got the equipment to get the bus back through the wormhole to Earth and asked the Tritovores to accompany them. Sorvin was reluctant at first, but soon warmed to the idea. At that moment however, a Stingray burst through the ceiling and devoured Praygat. Sorvin drew a gun in an attempt to avenge his comrade, but was eaten as well.(Planet of the Dead)