Mirrodin Besieged is a Magic: The Gathering expansion set scheduled to be released February 4, 2011. It is the second set of the Scars of Mirrodin block. This block will mark the return to the plane of Mirrodin, that was last visited in the Mirrodin block that concluded in 2004. The interim tagline for the set is "Steel Yourself for War." The Mirrodin Besieged Prereleases will be held on January 29–30, 2011. These will be different from other prereleases in that there will be special Mirrodin Besieged boosters that will be only available for the prerelease. These boosters will be composed exclusively of cards from either the Mirran or the Phyrexian faction. A player will have to choose one of these sides upon entering the prerelease and will receive corresponding boosters.
Check out these Mirrodin Besieged visual spoilers: