Planet 5

The fifth planet of the Sol system, possibly named Hestia (PROSE: Oblivion, The Rise & Fall of Señor 105) or Thyrop-Minerva (PROSE: The Taking of Planet 5) but most often called Planet 5, was the home planet of the "Star People", (PROSE: White Darkness) the Fendahl, and the Memeovore. (PROSE: The Taking of Planet 5)

At some point in the distant past, when the Great Old Ones were present across the universe and the Earth reptiles had gone into hibernation, the Star People, having created the Fendahl as genetically engineered servitors, were the first to be attacked by the creatures. The Old Ones fled from the Fendahl, which may have been weapons in a war being fought by the Old Ones. (PROSE: White Darkness)

Consequently, circa 12,000,000 BC, the Time Lords removed Planet 5 from the Sol system by placing it in a time loop. As a result, the fifth planet and all records of it were made permanently invisible. The Sol system's asteroid belt subsequently occupied the orbit of the planet, 107 million miles out from Earth, between Mars and Jupiter. (TV: Image of the Fendahl) This time loop enabled the last species left on Planet 5 to evolve into a lifeform that could feed on Fendahl, (PROSE: The Taking of Planet 5) the Memovore. (PROSE: The Book of the War)

During the War against the Enemy, Time Lords from the Eighth Doctor's subjective future planned to use a fleet of War TARDISes to undo the time barriers around Planet 5 in order to harness the Fendahl as a weapon against the Enemy; however, this instead resulted in the release of the Memeovore. (PROSE: The Taking of Planet 5)