The Skith General had witnessed the destruction of the Skith Ownworld by a mysterious Crimson Hand of great power. He and his ship's Mindcore decided to make use of the knowledge of time travel that the Mindcore had learned from the Tenth Doctor to construct their own time craft, the SKARDIS. They found, however, that the design required a time traveller to act as pilot.
To gain a pilot, the Skith General wreaked temporal havok in Sydney Australia in 2010, hoping to draw out the Doctor. They succeeded in drawing in the Tenth Doctor, Majenta Pryce, and the Skith Leader of Oppressor One. When the Skith Leader tried to take command, the Skith General informed him of the overall change of the Skith's situation, and threw him into the ship's fusion core.
The Mindcore was wary of the Doctor's cunning, and decided instead to use Majenta Pryce as the pilot they needed, turning her into the Skith Queen. Majenta's loyalty stayed with the Doctor, though, and she materialised the new SKARDIS over Sydney. UNIT forces there promptly blasted the Oppressor One — and the Skith General — into oblivion. (COMIC: The Age of Ice)