The metal plane of Mirrodin shines under the light of five suns ... but it's now tarnished by the deadly scourge known as Phyrexia. Besides the Mirran-Phyrexian conflict, the story also revolves around several planeswalkers. Elspeth Tirel returns while a new planeswalker by the name of Koth is introduced, a Vulshok native to Mirrodin (appearing as Koth of the Hammer). Venser (appearing as Venser, the Sojourner) and Tezzeret are also involved in the storyline.
Being set on Mirrodin, the expansion features themes and settings already known from that plane, such as Leonin (Cats), Vampires, Loxodon (Elephants), Elves, and the Human tribes of Vulshok, Sylvok, Auriok, Moriok and Neurok. Artifact creatures such as Golems and Myr also return.