Excroth

Excroth, located in the Excroth system, was the "favourite planet" of the Ninth Doctor. He took Rose Tyler and Jack Harkness there, but found that the planet had been destroyed. At the time they arrived, the Doctor said should have been the middle of the Second Excrothian Tetrachy, a period of unparalleled scientific enlightenment. The planet had been destroyed by a Dalek-made entropy engine, used by the Unon to prevent Excrothians from developing time travel. (COMIC: Weapons of Past Destruction)