The Sontarans come from a world with a much greater gravitational force than Earth called Sontar that caused them to evolve as a short stocky race of considerable physical power. A militaristic race by nature, the Sontarans would make there mortal enemies of the Rutans whom they have been locked in war with for at least fifty thousand years by 2008 AD Earth time.
To fight their almost endless war the Sontarans reproduce via cloning, producing millions of new troops on various worlds. This strength has also became there greatest weakness as there was a lack of acquiring nutrients for every clone. Every Sontaran has a probic vent at the back of their neck, and a single well placed blow can incapacitate or kill a Sontaran. Their war keeps them busy and away from the rest of the universe most of the time however there are occasions when the Sontaran Empire turns it’s eye towards achieving other goals, such as attempting to turn Earth into a new cloning world by polluting the atmosphere into a suitable state. The intervention by the Doctor in his tenth incarnation ended this alien invasion with the destruction of the Tenth Sontaran fleet.
The Time Warrior
The Sontarans` first known encounter with the Doctor was when a lone warrior named Linx crash-landed in a medieval village on Earth and claimed Earth for the Sontaran Empire. Using what’s left of his ships power, he manages to reach forward eight hundred years and capture scientist in order to have them repair his ship. Meanwhile the third Doctor who is currently with UNIT investigating the disappearances manages to pinpoint the era in which the scientists have arrived and pilots his TARDIS after them little knowing that a young journalist named Sarah Jane Smith has stowed aboard. After battling the Sontaran the Doctor and Sarah Jane manage to defeat Linx and travel back to there own time.
The next time the Sontarans would come against the Doctor would be in the distant future and another incarnation as the fourth Doctor, Harry Sullivan and Sarah Jane once again would face a lone Sontaran this time named Styre who is conducting experiments on astronauts on a barren Earth. Styre is acting on the orders of a for the Empire who is readying a fleet for an invasion. Styre ends up in single combat with the Doctor only to be defeated by one of his test subjects named Vural who intervenes. Styre, low on energy returns to his device to recharge only to die due to sabotage leaving the Doctor to inform the Marshall that there plans have failed and that the humans are aware of the proposed invasion, this information is enough to ward them off and costing them another bitter loss to the Time Lord.
The Invasion of Time
The next time the Sontarans would face the Doctor would be during there bold invasion of the Time Lords home world of Gallifrey. Aided by a corrupt Castellan the Sontarans manage to break though the planets defences which had been lowered by the Doctor who had returned with a plan of his own. Having the Time Lords hostage allowed the Doctor time to retreat to the depths of his Tardis and initiate the end game while his companion Leela deals with the remaining Sontarans with the help of Gallifreyen exiles. Tricking the Sontaran leader Stor into following him into the Tardis the Doctor defeats him using a terrible weapon of Time Lord design that erases him from time itself.
The Doctor met the Sontarans again in the TV episode The Two Doctors. In this episode the Doctor (in his sixth incarnation at the time) had to save his former second incarnation from the Sontarans who had joined forces with a band of Spanish military. The Sontarans were defeated again, although they continue to come into conflict with the Doctor far into the future.
The Sontarans` were a powerful force in the universe and were said to have conquered multiple galaxies in the name of the Sontaran Empire.
The Sontarans` power comes mostly from cloning soldiers to use in war. Millions of Sontaran clone soldiers were said to have been created every minute. However, with such an effective use of cloning, the Sontarans were often said to have limited resources and were always searching for more planets to conquer and use for creating clones.
The Sontarans are shown to have a limited power to time-travel.