The Magic: the Gathering (MTG) set Mirrodin Besieged (MBS) was released on Feb 4th, 2011. It includes 6 token cards.
Mirrodin Besieged is an expansion set in the Scars of Mirrodin block. An expansion set in Magic: The Gathering is a pool of cards released together and designed for play in the same environment. Standard cards and tokens in a set can be obtained at random through booster packs. Sometimes a set will contain promo tokens that are given away as prizes at Friday Night Magic (FNM) or special pre-release events.