Metathran

Metathran is a creature type used for cards that depict a blue-aligned race created in Urza's Bloodline Project. Part of Urza's plans to repel the inevitable Phyrexian Invasion, they were solely meant as soldiers. Dubbed the "Metathran" in honor of the long-lost Thran civilization, Urza's warriors were genetically engineered to be decisive, unerring and obedient, with superhuman combat skills and tactical awareness. The Metathran had a distinctive light-blue hue and a tall, gangly appearance. They appeared male, but in fact had no gender, as they would have no need to procreate. Intended to fight the Phyrexian menace and nothing else, the Metathran were freely expendable, and none survived the war.

The cards as they appeared in the Urza's block and Invasion block didn't have the subtype Metathran. It was later realised that a non-human race should have its own subtype. This was fixed in the Grand Creature Type Update

Notable Metathran

Most of the Metathran were designed to blindly follow orders, however, two generals had been specifically designed to act on their own. Thaddeus and Agnate had a symbiotic, near-telepathic connection to each other and depended on each other to function.

Kor origins controvery

According to a comment by Urza on Bloodlines, Rath's Kor are derived from his Metathran stock, having somehow been stolen from him. However, more recent statements by Doug Beyer contradict this claim.