Tythonus

Tythonus was the native planet of the Tythonians. It was rich in metals and has at least some forms of plants, though these plants were becoming rare.

The Tythonians had hoped to trade with Chloris, but the first person their ambassador Erato encountered on arriving in his eggshell-like ship was Adrasta, who took his communicator device and trapped him in the Pit so as to preserve her monopoly on metal. Erato retrieves his communicator and kills Adrasta.

He then warns the Doctor that the Tythonians have set a neutron star on a collision course with Chloris in retaliation for his imprisonment. With the Doctor's help he is freed from the Pit and, out in space, spins an aluminium shell around the star, allowing for it to be pulled off course by the TARDIS's gravitational tractor beam and thus saving Chloris.

(DW: The Creature from the Pit)