Symbios

 was a sentient planet, a living world imbued with a living energy known as the Locus, the life force of the planet.

Symbios had two moons and stars were visible in its sky by day. Its landscape included rainforests that had no birds or insects, bone-like trees, swamps of blood, and arterial tunnels. As long as the Locus survived, nothing died on the world.

The Sixth Doctor visited Symbios, after having previously saved the planet from an invasion by the Drahvins. (AUDIO: The Crimes of Thomas Brewster)

Symbios