Levithia was a planet in the Seven Systems.
When the emperor of the Levithian Empire was killed by his brother Grath, his children, Asher and Ella, fled Levithia to Gallifrey to escape a similar fate. When the twins came of age, the emperor's advisor, Rigel came for them and returned them home, where they took back their empire. (PROSE: The Twins in the Wood)
The planet was in league with the Cyrrhenic Empire. It was originally led by Graff Vynda-K, but when he went off to fight in the Frontier wars, his half-brother took over the throne. When Graff Vynda-K attempted to take back his kingship, the people did not support him, the Alliance refused to back him and his mind snapped. He went off to search for a means to take back the planet by force. (TV: The Ribos Operation)
Levithia was one of the planets that did not accept the format of star map produced by Kasterborous, preferring to make their own system. (PROSE: Short Trips: Zodiac)