Mirrodin, originally known as Argentum, was created by the Planeswalker Karn. Mirrodin's caretaker Memnarch slowly went mad, abducting mortals from across the Multiverse to populate the plane. On this world of metal, the inhabitants brought to Mirrodin were shaped by the harsh environment and became masters of artifacts and weaponry.
Karn was the bringer of the Phyrexian oil to Mirrodin, which began the slow process of transforming the creatures it touched deep beneath the world's surface. Slowly losing his mind, Karn became the Father of Machines and the leader of Phyrexia. The slow spread soon became an active campaign to alter, or compleat, the world of Mirrodin. The Mirrans fought many battles, but they soon were overwhelmed by the Phyrexian forces.
Even the Planeswalkers Koth, Elspeth, and Venser could not turn the tide, and Venser sacrificed his life to restore Karn to sanity. But by then, not even the creator of Mirrodin could stop the Phyrexian machine. Now the Praetors—some of Karn's top lieutenants—and their factions fight for power amongst themselves while the natives struggle daily to survive.