Ruta III
From Tardis Wiki, the free Doctor Who reference
Ruta III is a cold world, though still within a range tolerable to humans. The only known inhabitants are the Rutan Host, which evolved from aquatic lifeforms.It is probable that the Doctor has traveled here. It is also unknown if the Sontarans ever attempted to take the planet.The Queen of the Rutans lives on the planet and without her the Rutan Host would fall apart.