The Rutans are the sworn enemies of the Sontarans. In basic appearance, the Rutans are similar to jellyfish but they have the remarkable ability to shapeshift at will, however, a Rutan cannot create a new form it can only steal the shape of a creature it has killed.

Rutans are very strong, able to carry with ease the weight of a human while climbing a sheer wall or cliff. They are amphibious and are oblivious to extreme cold. Rutans can only be killed by weapons that burn, disintegrate, or freeze them solid; ordinary chemical explosive guns or lasers have no effect on them. They must be literally blown to bits, fried, or freeze-dried.

Being a parasitic race, Rutans have the unpleasant habit of feeding off the life energy of other beings. This process is invariably fatal to the unfortunate victim chosen as a food source. They kill their prey on contact with a powerful oranically-produced electric charge. Though Rutans in other forms can use ranged weapons, they seem to delight in using this method.