Controlling another player

Controlling another player's turn are rules written specifically for one card, Mindslaver, although Planeswalker card Sorin Markov now makes this ability available from a new source. Mindslaver was designed by Mark Rosewater. It was originally conceived as a card for Tempest, called Helm of Volrath but R&D didn't like the original card. It was then going to be put in Unglued 2, but that set was put in indefinite hiatus. It finally made it into Mirrodin with the blessing of Paul Barclay, the rules manager.

From the ()

Rulings for Mindslaver

• You can see everything that player can see but you normally could not. This includes that player's hand, face-down creatures, and any cards in his or her library that he or she looks at.
• You control the entire turn, from the untap step to the cleanup step. The other player doesn't lose life because of mana burn at any time during that turn.
• You could gain control of your own turn using Mindslaver, but gaining control of your own turn doesn't really do anything and you can still lose life to mana burn.
• You don't control any of the other player's permanents, spells, or abilities.
• You can't make the other player concede. A player can choose to concede at any time.
• You get to make every decision the other player would have made during that turn. You can't make any illegal decisions or illegal choices -- you can't do anything that player couldn't do. You can spend mana in the player's mana pool only on that player's spells and abilities. The mana in your mana pool can be spent only on your spells and abilities.
• You choose which spells the other player plays, and make all decisions as those spells are played and when they resolve. For example, you choose the target for that player's Shock, and what card that player gets with Diabolic Tutor.
• You choose which activated abilities the other player plays, and make all decisions as those abilities are played and when they resolve. For example, you can have your opponent sacrifice his or her creatures to his or her Nantuko Husk or have your opponent's Timberwatch Elf give your blocking creature +X/+X.
• You make all decisions for the other player's triggered abilities, including what they target and any decisions made when they resolve.
• You choose which creatures attack and how those attacking creatures assign their combat damage.
• You also make choices for your own permanents, spells, and abilities as usual.
• You can't make any decisions that aren't called for or allowed by the game rules, or by any cards, permanents, spells, abilities, and so on.
• If you make another player play Shahrazad, you don't control any of that player's turns in the subgame, but you continue to control the current turn once the subgame is completed.