Huwyma

In an alternate universe, Huwyma was a Rutan world which was conquered by Sontarans. They turned Huwyma into a colony planet, and created factories to manufacture neutron weapons. In retaliation, the Rutan Host destroyed the planet with an anti-matter converter.

The destruction of Huwyma caused tension at the Rutan-Sontaran peace conference, which occurred three months later. The Doctor brought up a hologram of the planet. By this time, Huwyma's seas had dried out and it could not support life. (PROSE: The Infinity Doctors)