The Thran, an extinct race to which the Phyrexians belonged before they became half-mechanical monstrosities, once ruled Dominaria. They created powerful artifacts long before the times of Mirrodin or the Urza Saga block, and crafted ornate designs into their creations.
Buried in a Magic artist's style guide from the Urza's Saga days is this tidbit about the Thran: the Thran symbol, an icon representing the Thran culture and technology (see the symbol at right). This symbol is depicted in a few Magic cards; for example, see the art of Urza's Legacy's Thran War Machine and Urza's Saga's Thran Quarry, below.
Learn more about the Thran in The Thran, a novel by J. Robert King.