Thoros-Beta was a rocky planet inhabited by the Mentors and twin planet to Thoros Alpha. The many oceans of Thoros-Beta were pinkish and the sky a greenish blue. There was also a large gas giant within sight of the surface. Most of the settlements were underground and located within caverns.
Seas on Thoros-Beta included the Sea of Turmoil, the Sea of Despair and Longing and the Sea of Sorrows. A location called Brak was known for its islets. (TV: Mindwarp)
The Fifth Doctor was aware of Thoros Beta and made an effort to avoid it during his travels because of its "garish" colour scheme. (AUDIO: Zaltys)