Planet (Underworld)

The unnamed planet formed by the gravitational pull of debris floating through a spiral nebula assembled into a nearly hollow planet around the hull of the ancient Minyan spaceship called the P7E.

Inside, it resembled a series of caverns and caves with an atmosphere breathable by humanoids. A second Minyan ship, the R1C, crewed by near-immortals, who had extended their lives by regeneration, as well as the Doctor and his companions K9 and Leela once landed there. When the Doctor and Leela first stepped onto the planet, he called it "the Underworld", almost certainly referencing its similarity to a place in Greek myth. There, they found the other last surviving Minyans, who had lived there lives enslaved to the computer known as the Oracle. These inhabitants — Guards, "Trogs", and Seers alike — knew nothing of their origins, let alone that nuclear war had destroyed their original homeworld.

After the defeat of the Oracle, the inhabitants headed aboard the R1C for a new planet, Minyos II. (DW: Underworld)