Throneworld

A Throneworld was an important planet in an empire, presumably serving as a capital.

Pluvikerr was the Throneworld of the Gubbage Cone Empire. (PROSE: The Crystal Bucephalus) The Master later stole a Vortex Cloak from the ruins of the Gubbage Cone Throneworld. (PROSE: The Quantum Archangel)

Phaester Osiris was the Throneworld of the Osirian Court. (AUDIO: The Ship of a Billion Years, PROSE: The Sands of Time)

In an alternate timeline where Rassilon and the Cybermen invaded all of time and space, all the throne planets of the Sontaran Empire were destroyed. (COMIC: Supremacy of the Cybermen)