Titan III

Titan III, or Titan 3, was a barren and desolate planet, though the Sixth Doctor also called it an asteroid on one occasion. It was possibly the most remote planet in the Mutter's Spiral, so far below the plane of the ecliptic that no one ever came closer than a hundred thousand light-years. (PROSE: The Quantum Archangel)

It was the location of a safehouse used by Azmael after abducting Romulus and Remus Sylvest in 2310. In his pursuit of the twins, Hugo Lang was shot down over the planet and crashed there. He was rescued by the Sixth Doctor, who had come to Titan III to become a hermit and atone for almost killing Peri Brown shortly after his regeneration. The Doctor and Peri were captured by Azmael and imprisoned, but unknown to him, Noma had set the base to self-destruct. However, the Doctor and his friends escaped and pursued Azmael to Jaconda. (TV: The Twin Dilemma)