Vural was one of a group of GalSec colonists stranded on Earth after their ship was destroyed while answering a fake distress signal. Styre performed cruel experiments on Vural to assess human physical limitations.
He tried to make a deal with Styre in exchange for his own life, letting Styre place a small transmitter on him which allowed the Sontaran to spy on his every movement. Accused of betraying his crew, he later proved he had a better nature than he let on when he sacrificed his life to save that of the Fourth Doctor.
He wrestled with Styre, which prevented him from cutting open the Doctor with a hunting knife stolen from the colonists. Styre quickly broke free from Vural's grip and cut him down instead with a single slash. (TV: The Sontaran Experiment)