Sontarans are built and bred for war, a subject at which they are masters after countless years of conflict with the Rutans, a sort of intelligent, phosphorescent green jellyfish. The Sontarans' home planet, Sontar, has a high gravity, and the species' stocky, heavily muscled bodies reflect this. Their manlike form is encased in flexible, gunmetal-coloured space armour; a smooth, dome-like helmet with narrow eye holes provides complete protection for the head. A translation box on a wide belt allows a Sontaran to understand and speak any language.
By human reckoning, Sontarans are ugly: they have smooth-skinned, brown dome-like heads, with squat features and small red piggy eyes. Coarse bristles sprout in tufts from their ears and chins. A superstitious people might easily believe them to be goblins. Sontarans have only two fingers on each hand and opposable thumbs.
Although Sontaran technology is highly advanced, bordering on limited time travel, it is geared to war. Much of the time, Sontarans are encountered individually and are usually scouts sent out to reconnoitre terrain or analyse the physical and mental weaknesses of the enemy. Scouts have spherical spaceships, about 5 metres in diameter, that are equipped with the necessary laboratory equipment to assist their in tasks and which also act as the control centre for their operations. Wherever there is a scout, a full invasion force is sure to be close by.
Sontarans are clones: all of them look alike. They consider all other methods of reproduction as weaknesses, pointing out that up to a million cadets are hatched at a time at the Sontaran Military Academy, enabling the species to sustain tremendous casualties in war. Sontarans act alike, too: they respect military hierarchy and are used to ordering people about; Sontarans have little skill at negotiation. It must not be forgotten that although they are a martial race and relish even other people's conflicts, they have a high intelligence.