Before the Rutans destroyed Sontara in the 26th century, Stave and his troops were able to escape with the Sontaran racepool on his flagship, the Warburg.
He went to the Pandora Spindle to use its genetic facilities to create new Sontarans. However, they were pursued by the Rutans and their unwitting allies, a group of Pureblood Sontarans. After the Rutans duplicity was revealed by the Seventh Doctor, all the Sontarans united to repel the Rutans.
The Doctor's price for his help was to have all knowledge of humanity removed from the racepool, giving it relief from Sontaran encroachment for centuries to come. Stave agreed, cognisant of the fact that he had much rebuilding to do. He transported the humans on Pandora back to Terran Federation space, and began the long process of rebuilding the Sontaran Empire, using the planet beneath the station as their new homeworld. (COMIC: Pureblood)