Probic vent

The probic vent was a tube on the back of a Sontaran's armour.

Information
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. Raw plasma was fed into the vent to nourish them. (DWM: 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. (DW: The Time Warrior) A lesser blow could cause them pain and/or stun them. (DW: The Sontaran Stratagem) An arrow (DW: The Time Warrior) or a thrown knife (DW: The Invasion of Time) would almost certainly prove deadly.

Sontarans did not consider this a weakness however, since it meant that they must always face their enemy in battle, nor could they be cowardly or retreat. (DW: The Time Warrior, The Sontaran Experiment)

Strangely, some Sontarans had an extra part on their helmets that covered the probic vent, offering a defence from these attacks. (NA: Shakedown)

The energies directed through the vent seemed to be at least partly electrical in nature. When Chrissie Jackson jammed the metal tip of one of her high heels into Kaagh's vent, she received an electric shock. (SJA: The Last Sontaran)

List of weapons used to strike a probic vent

 * A metal pole (DW: The Time Warrior)
 * A bow and arrow (DW: The Time Warrior)
 * Knives (DW: The Invasion of Time)
 * A squash ball (DW: The Sontaran Stratagem)
 * A hammer (DW: The Poison Sky, The End of Time)
 * A high-heeled shoe (SJA: The Last Sontaran)
 * A sword (DW: A Good Man Goes to War)
 * A loose wooden plank (VG: The Gunpowder Plot)
 * Marbles fired from a slingshot (VG: The Gunpowder Plot)