A small Sontaran attack force arrives to wreak havoc...
In "The Invasion of Time" the Doctor returns to Gallifrey, claims his rights and is inaugurated President. It soon turns out that he has led a group of aliens called Vardans to the planet to eradicate them completely. After they are destroyed, the Sontarans take their opportunity and follow them in their invasion until they are destroyed by the Doctor.
The size of their army numbers in hundreds of millions and they can clone a million new soldiers every four minutes. In this story we finally see more than one Sontaran on screen at the same time, and they have three fingers on each hand as they did in their debut story. The leader of this group, called Stor, has a helmet which bears a bold version of the insignia first seen on Linx's helmet where it was made up of dots. Stor's helmet has the largest eye-holes so far seen, and bears a very thick rim which differs to his troops.