Ritskaw

Ritskaw was a Sontaran Commander. He was an "old friend" of Psychic Surveyor Kragar.

Biography
After finishing his investigation of the Flux, Kragar called Ritskaw on his ship. Ritskaw was excited by the news of a greater cataclysm than had ever been known, deciding to use the opportunity to strike other species while they were at their weakest; he soon ordered an attack just as Earth was bearing the brunt of the Flux cloud. (TV: The Halloween Apocalypse)

Behind the scenes

 * Ritskaw's name is misspelled as "Rishaw" in the credits for War of the Sontarans.