Controlling another player

Controlling another player is an effect on a very small number of cards which extends the concept of taking control of a permanent and its actions, to an entire player and their actions.

Description

The rules governing this effect are complex and written specifically for the first card to cause this effect, Mindslaver. The cards Sorin Markov, Worst Fears, Emrakul, the Promised End, Cruel Entertainment, and Opposition Agent now make this effect available from other sources. Most of these cause the player to be controlled for one full turn. Controlling another player essentially matches the concept and effect of Word of Command, so its Oracle text was updated to use it, although the target is only controlled while it and another spell are resolving, unlike other instances. Kindslaver is a parody of this ability.

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.

Rules

From the glossary of the Comprehensive Rules (June 7, 2024—Modern Horizons 3)

Control Another Player

To make all choices and decisions that player is allowed to make, or is told to make, by rules or by any objects. See rule 720, “Controlling Another Player.”

From the Comprehensive Rules (June 7, 2024—Modern Horizons 3)

• 720. Controlling Another Player
  • 720.1. Some cards allow a player to control another player during that player’s next turn. This effect applies to the next turn that the affected player actually takes. The affected player is controlled during the entire turn; the effect doesn’t end until the beginning of the next turn.
    • 720.1a Multiple player-controlling effects that affect the same player overwrite each other. The last one to be created is the one that works.
    • 720.1b If a turn is skipped, any pending player-controlling effects wait until the player who would be affected actually takes a turn.
  • 720.2. Two cards (Word of Command and Opposition Agent) allow a player to control another player for a limited duration.
  • 720.3. Only control of the player changes. All objects are controlled by their normal controllers. A player who’s being controlled during their turn is still the active player.
  • 720.4. If information about an object in the game would be visible to the player being controlled, it’s visible to both that player and the controller of the player. If information about cards outside the game would be visible to the player being controlled, it’s visible only to that player, not the controller of the player.

    Example: The controller of a player can see that player’s hand and the face of any face-down creatures they control.

  • 720.5. While controlling another player, a player makes all choices and decisions the controlled player is allowed to make or is told to make by the rules or by any objects. This includes choices and decisions about what to play, and choices and decisions called for by spells and abilities.

    Example: The controller of another player decides which spells that player casts and what those spells target, and makes any required decisions when those spells resolve.

    Example: The controller of another player decides which of that player’s creatures attack, which player or planeswalker each one attacks, what the damage assignment order of the creatures that block them is (if any of the attacking creatures are blocked by multiple creatures), and how those attacking creatures assign their combat damage.

    • 720.5a The controller of another player can use only that player’s resources (cards, mana, and so on) to pay costs for that player.

      Example: If the controller of a player decides that the controlled player will cast a spell with an additional cost of discarding cards, the cards are discarded from the controlled player’s hand.

    • 720.5b The controller of another player can’t make choices or decisions for that player that aren’t called for by the rules or by any objects. The controller also can’t make any choices or decisions for the player that would be called for by the tournament rules.

      Example: The player who’s being controlled still decides if they will leave to visit the restroom, trade a card to someone else, agree to an intentional draw, or call a judge about an error or infraction.

  • 720.6. The controller of another player can’t make that player concede. A player may concede the game at any time, even if they are controlled by another player. See rule 104.3a.
  • 720.7. The effect that gives control of a player to another player may restrict the actions the controlled player is allowed to take or specify actions that the controlled player must take.
  • 720.8. A player who controls another player also continues to make their own choices and decisions.
  • 720.9. A player may gain control of themselves. That player will make their own decisions and choices as normal.

Rulings for Mindslaver

• Only lets you make decisions that the player would actually make. If another effect allows another player to make decisions that would normally be made by that player, such as having another player decide how combat damage is dealt, then the other effect takes precedence.
• You could gain control of yourself using Mindslaver, but gaining control of yourself doesn’t really do anything.
• 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 casts, and make all decisions as those spells are cast 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 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 cast Shahrazad, you don’t control that player in the subgame, but you continue to control them once the subgame is completed.
• You choose which activated abilities the other player activates, and make all decisions as those abilities are activated and when they resolve. For example, you can have your opponent sacrifice their creatures to their Nantuko Husk or have your opponent’s Timberwatch Elf give your blocking creature +X/+X.
• You control them for the entire turn, from the untap step to the cleanup step.
• Controlling a player doesn’t allow you to look at that player’s sideboard. If an effect instructs that player to choose a card from outside the game, you can’t have that player choose any card.
• While controlling another player, you can see all cards in the game that player can see. This includes cards in that player’s hand, face-down cards that player controls, and any cards in that player’s library the player may look at.