Sontaran space armour

Sontaran space armour, identified by Jingo Linx, was the distinctive battle armour which was worn by the Sontarans. Several variants of the space armour existed throughout the Sontarans' long history of war, appearing in varying time periods. (TV: The Time Warrior, HOMEVID: Return of the Sontarans, TV: The Sontaran Stratagem / The Poison Sky) They were characterised by the Thirteenth Doctor as protective armoured suits. (TV: War of the Sontarans)

The newly cloned Strax was provided with Mark VII Battle Armour, complete with a Mark VII Tactical Helmet. (PROSE: A Soldier's Education)

Helmet
Though Sontarans generally wore helmets, some could choose to go without their helmet in what was referred to being "open-skinned". (TV: The Sontaran Stratagem) The helmets of Sontarans of the Special Assault Squad, such as Kaagh, could be automatically retracted into their armour at will. (TV: The Last Sontaran)

Probic vent
A common and most vulnerable feature of Sontaran space armour was the probic vent. At least partially artificial, the probic vent took the form of a small metallic tube entering the back of the Sontaran's neck. This vent was normally used by the Sontarans to feed directly on energy to "recharge" rather than eating. (COMIC: The Betrothal of Sontar) The vent was also a major weakness. A blow to the probic vent could knock Sontarans unconscious or even kill them. (TV: The Time Warrior)

Variants
One type of armour resembled a thick and bulky grey space suit. The helmets was dome-shaped and almost featureless except for two eye holes and a small, flat crest running from the forehead to the back of the neck. They generally carried around their rod-like weapon and a translating device. About the only thing that could penetrate this armour was coronic acid, as was used in 2371 by Raghi defence forces. (PROSE: Lords of the Storm) Such suits were worn by Jingo Linx in the 13th century, (TV: The Time Warrior) Group Marshal Stike and Major Varl in the 1980s, (TV: The Two Doctors) in the 31st century, (AUDIO: Terror of the Sontarans) Field Major Styre and his Marshal in 16087, (TV: The Sontaran Experiment, AUDIO: Wirrn Isle) Sontaran Special Space Service forces who were led by Commander Stor in the invasion of Gallifrey. (TV: The Invasion of Time)

The ranks of individual Sontarans were generally not prominently displayed on the uniform. The Marshal above Styre sported two large spiky disks on the front of his collar. (TV: The Sontaran Experiment) Commander Stor wore a larger collar than his troops and had a white, three-pointed, crown imprinted on his helmet. (TV: The Invasion of Time) Group Marshal Stike had white braiding on his shoulders, akin to epaulettes. (TV: The Two Doctors)

Sontaran ship crews wore blue space armour, while Sontarans of the medical and environmental divisions wore green armour. (PROSE: Lords of the Storm)

Other Sontarans had blue, less flexible, armour. This armor was no match for bullets used by UNIT during the 2009 Sontaran invasion of Earth. (TV: The Poison Sky) Such armour was worn by Sontarans who attempted to participate in the Last Great Time War, (AUDIO: The Sontaran Ordeal, The Eternity Cage) representatives of the Alliance in 102, (TV: The Pandorica Opens) the early 17th century, (GAME: The Gunpowder Plot), the early 21st century, (TV: The Sontaran Stratagem/The Poison Sky) the 26th century, (PROSE: The Taking of Chelsea 426) and the Siege of Trenzalore. (TV: The Time of the Doctor) In addition, this type of armour was worn by Strax, who served as a nurse in the Battle of Zaruthstra in 4037. (TV: A Good Man Goes to War)

On the bulky, blue armour, badges of rank were more clearly visible and consisted of various symbols set into the right-hand side of the front of the collar. Generals such as Staal wore five diamonds in a crown-shaped pattern. Commanders such as Skorr sported three diamonds in a similar pattern. The lowest rank of this badge design was Lieutenant, displayed by a single diamond in the middle of the badge, shown on Lieutenant Skree, an operations officer. (TV: The Sontaran Stratagem/The Poison Sky)

A Sontaran outside a Sleazy Bar wore identical bulky armour but coloured white. (COMIC: World Without End) Sontarans loyal to wore similar bulky armour but coloured black. Suicide Specialists wore bulky red armour with a chest containing an eschatomic warhead. (COMIC: The Judas Goatee)

Time traveling Sontarans who sought to exploit the Flux in 2021 wore dark, bulky armour. (TV: The Halloween Apocalypse)

Sontaran soldiers seen in the late 26th century wore armour with red helmets while Commander Steg wore a gold helmet. These Sontarans had an extra part on their helmets that covered the probic vent, offering a defence from attack. (HOMEVID: Return of the Sontarans, PROSE: Shakedown)

Individual cases
Strax was a rare example of a Sontaran who regularly appeared outside of his armour; while serving as the butler of the Paternoster Gang, Strax wore human clothing. However, he did assume his Sontaran space armour when occasions called for it, such as when fighting the followers of Winifred Gillyflower. (TV: The Crimson Horror)

A Sontaran resident of the trap street in central London wore Sontaran space armour. Because of the lurkworms' misdirection circuit, however, the Sontaran appeared as a human in contemporary clothing. (TV: Face the Raven)

Behind the scenes

 * The Sontarans, waging a campaign against history, appear in their bulky blue armour in the video game Legacy. In addition, an axe-wielding variant is seen wearing a blue cape matching their helmet.