Tryska was a subordinate of Jastrok.
She observed Kate Stewart and Petronella Osgood entering a Silurian nest in Greece. On following them, she hunted the UNIT troops who were Kate's backup. She then went into the caves, to stop Kate and get a machine that induces fear in humans. She attacked Kate and poison her. Sam Bishop followed her and attacked her hoping that he had destroyed her machine. She decided to destroy the base, but couldn't escape due to Osgood and Sam Bishop placing a snake calling device on her and she died in the explosion. (AUDIO: Retrieval)