The Tythonian ambassador, Erato, was piloting a Tythonian ship when he travelled to Chloris. There he was imprisoned, separating him from the ship. His captor, Lady Adrasta, took an interest in finding out the ship's origin and purpose. She went so far as to execute one of her men who had failed to deduce what it was. The Fourth Doctor suggested that it was an egg, but then fled from Adrasta who turned to Romana for answers.
When Erato was freed, he returned to his ship and used it to help the Doctor prevent a neutron star from destroying Chloris' sun. As the Doctor used his TARDIS to slow it, Erato weaved an aluminium shell around it using the ship. This halted the star. (TV: The Creature from the Pit)