Mutavault | Magic: The Gathering
Formats Mutavault is Legal in
Official Oracle Text for Mutavault
: Mutavault becomes a 2/2 creature with all creature types until end of turn. It's still a land.
Official Rulings for Mutavault
8/1/2008 : A noncreature permanent that turns into a creature can attack, and its abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of his or her most recent turn. It doesn't matter how long the permanent has been a creature.
7/1/2013 : Examples of creature types include Sliver, Goblin, and Soldier. Creature types appear after the dash on the type line of creatures.