Styre was a Sontaran Field Major with the G3 Military Assessment Survey. He reported to an unnamed Marshal.

At some point he was ordered by the Grand Strategic Council to make an assessment of human physical limitations.

Apparently Styre's mission was of some urgency, as it was noted by his superior that "the entire invasion fleet" was held up by his delay. The Doctor claimed they were probably going to invade the entire Mutter's Spiral.

He lured eight human soldiers from GalSec to an abandoned Earth to subject them to experiments. Amongst the things he tested were their reaction to fear, muscular strength, and the human breast case resistance to pressure, using a gravity bar. Styre noted that humans were highly dependent on fluids and if they did not drink, they started to lose mental and motor skills in as few as three days, which he thought should be exploited.

He was defeated by the Fourth Doctor, Sarah Jane Smith, and Harry Sullivan. Styre died after connecting his probic vent to his ship. Harry had earlier sabotaged it, so rather than absorbing energy from the ship, the ship drained Styre's energy. (TV: The Sontaran Experiment)

As Sarah Jane noted, Styre appeared identical to Linx in most ways. However, unlike most Sontarans, Styre had five rather than three fingers on each hand. Sarah Jane's reference was to show that the Sontarans were cloned and that all are nearly identical.