Planet of origin: Tthe moon of planet Sontar (AKA Sontara), a planet with 5 times Earth's gravity, in the Milky Way Galaxy.
Several thousand years ago, at a time when the Kaveetch people, a humanoid species native to Sontar which had developed an advanced space faring civilisation, were losing a war against the Rutan Host and coming close to extinction, they established on the moon of their homeworld an infrastructure allowing them to mass produce clones genetically engineered to excel in the art of war. The belligerent and militaristic Sontaran clones managed to fight off the Rutan assaults and got rid of the remaining Kaveetch they deemed inferior to themselves. The existence of their creators was eventually erased from their history. Their revised origin presentedand rewritten as them as a species split into clans, which fought amongst themselves until the arrival of a common foe, the Rutans, forced them into unity.
The Sontarans are grey-brown skinned greenblooded humanoids. They have have large potato-like neckless heads, three fingered hands and short stocky bodies. Due to the high gravity of the moon of Sontar where they were first created, they have great strength and resilience in lower gravity environments. Although extremely resistant, they are vulnerable to coronic acid. They absorb energy via the probic vent on the back of their necks. A sudden blow to the vent would stun them while the penetration of a sharp object into it will kill them. Tampering with the energy feed could also lead to a reversal effect that could destroy them from the inside out.
The Sontarans are capable of creating around a million clones every four minutes, grown in vats and were nourished by sezerfine gas, and are therefore able to sustain massive casualties. They can also heal their wounds with a stubby tubular device called a tissue rectifier.
The Sontaran technology has allowed them to miniaturised FTL technology to a point where small one men craft have interstellar range. Whatever their size, their starships are usually spherical. They use teleportation technology using generators situated at area of materialisation and dematerialisation, and limited time travel technology which they inherited from the Kaveetch. By the 13th centuray, they used osmic projection. In the 20th century, they started making attempts to obtain more effective time travel
Sontarans also used mind control individuals, either taking over their minds through rheon carbine, a thin, metallic weapon, which was designed to optimally fit the Sontaran hand, and was used for energy projection and hyponotism; or controlling them with devices attached to the neck.
Sontarans used a Base-6 counting system.
They are known to have visited Earth during the ancient Egyptian civilisation, where he was worshipped as a god until the humans learned that he planned to destroy Earth, at whihc point he was buried alive in a pyramid.
In the 13th century, a scout, landed in England and claimed it for the Sontaran Empire. He proceeded to make an alliance a local warlord, and to transport scientists from the late 20th century into the past using his osmic projection. He would then hypnotise them in order to make them work on his ship.
From that point on, several sontaran scoutships eithet landed or crashed on Earth, most of the time with fatal results, like the one that crashed in Tunguska in the 1920ies. But it is not until 2009 that an all out invasion of the planet was attempted. As the Sontarans were momentarily losing their eternal war against the Rutans, the Tenth Sontaran Battle Fleet made plans to convert Earth into a cloning world but failed, resulting in the destruction of their fleet.
Source: Doctor Who universe. (TV: The Two Doctors, TV: The Last Sontaran; The Time Warrior, The Sontaran Experiment, The Sontaran Stratagem / The Poison Sky)