Master Thief | Magic: The Gathering
Formats Master Thief is Legal in
Official Oracle Text for Master Thief
Official Rulings for Master Thief
9/22/2011 : If Master Thief ceases to be under your control before its ability resolves, you won't gain control of the targeted artifact at all.
9/22/2011 : If another player gains control of Master Thief, its control-change effect ends. Regaining control of Master Thief won't cause you to regain control of the artifact.