505.3. Because every split card consists of two halves with different colored mana symbols in their mana costs, each split card is a multicolored card while it’s not a spell on the stack. While it’s a spell on the stack, it’s only the color or colors of the half being played.

505.4. Although split cards have two playable halves, each split card is only one card. For example, a player who has drawn or discarded a split card has drawn or discarded one card, not two.

505.5. An effect that asks for a particular characteristic of a split card while it’s in a zone other than the stack gets two answers (one for each of the split card’s two halves).

Example: Infernal Genesis has an ability that reads, “At the beginning of each player’s upkeep, that player puts the top card from his or her library into his or her graveyard. He or she then puts X 1/1 black Minion creature tokens into play, where X is that card’s converted mana cost.” If the top card of your library is Assault/Battery when this ability resolves, the game sees its converted mana cost as “1, and 4.” You get five creature tokens.

505.6. An effect that performs a positive comparison (such as asking if a card is red) or a relative comparison (such as asking if a card’s converted mana cost is less than 2) involving characteristics of one or more split cards in any zone other than the stack gets only one answer. This answer is “yes” if either side of each split card in the comparison would return a “yes” answer if compared individually.

An effect that performs a negative comparison (such as asking if cards have different names) involving characteristics of one or more split cards in any zone other than the stack also gets only one answer. This answer is “yes” if performing the comparable positive comparison would return a “no” answer.

If an effect performs a comparison involving multiple characteristics of one or more split cards in any zone other than the stack, each characteristic is compared separately. If each of the individual comparisons would return a “yes” answer, the whole comparison returns a “yes” answer.

Example: Void reads, “Choose a number. Destroy all artifacts and creatures with converted mana cost equal to that number. Then target player reveals his or her hand and discards all nonland cards with converted mana cost equal to the number.” If a player plays Void and chooses 1, his or her opponent would discard Assault/Battery because the game sees its converted mana cost as “1, and 4.” The same is true if the player chooses 4. If the player chooses 5, however, Assault/Battery would be unaffected.

505.7. If an effect instructs a player to name a card and the player wants to name a split card, the player must name both halves of the split card.

506.1. Some cards allow players to play a Magic subgame. A “subgame” is the game created by the card’s effect. The “main game” is the game in which the spell or ability that created the subgame was played. The main game is temporarily discontinued while the subgame is in progress. It resumes when the subgame ends.

506.2. Any main-game abilities that trigger while the subgame is in progress aren’t put onto the stack until the subgame is completed.

506.3. To start the subgame, each player removes his or her library from the game face down. It becomes that player’s deck in the subgame. Abilities that trigger on cards being removed from the main game face down will trigger.

506.3a A player’s deck in the subgame may have less than the minimum number of cards. If a player’s deck contains less than seven cards, the player will lose the game as soon as it starts, even if he or she mulligans. (See rule 420, “State-Based Effects.”)

506.4. The subgame proceeds like a normal game. Randomly determine which player goes first.

506.5. All objects in the main game and all cards outside the main game are considered outside the subgame (except those specifically brought into the subgame). All players not currently in the subgame are considered outside the subgame.

506.5a Some effects can bring cards into a game from outside of it. Cards brought into a subgame from a main game are considered to be removed from the main game. Abilities in the main game that trigger on objects being removed from the main game will trigger.

506.6. At the end of a subgame, each player puts all objects he or she owns that were brought into the subgame into his or her library in the main game, then shuffles that library. Cards removed from the game in the subgame are not put into the player’s main-game library. Instead they remain removed from the game in the main game.

Example: If a card was brought into the subgame either from the main game or from outside the main game, that card will be put into its owner’s main-game library when the subgame ends.

506.7. If another subgame is created during a subgame, there can be multiple subgames and main games. Each main game has one subgame, and each subgame has one main game. In this case, some games will be considered both a main game and a subgame at the same time.

507.1. One card (Mindslaver) allows a player’s turn to be controlled by another player. This effect applies to the next turn that the affected player actually takes. The entire turn is controlled; the effect doesn’t end until the beginning of the next turn.

507.1a Multiple turn-controlling effects that affect the same player overwrite each other. The last one to be created is the one that works.

507.1b If a turn is skipped, any pending turn-controlling effects wait until the player who would be affected actually takes a turn.

507.1c Only the control of the turn changes. All objects are controlled by their normal controllers.

507.2. If information about an object would be visible to the player whose turn is controlled, it’s visible to both that player and the controller of the turn.

Example: The controller of a player’s turn can see that player’s hand and the identity of any face-down creatures he or she controls.

507.3. The controller of another player’s turn makes all choices and decisions that player is allowed to make or is told to make during that turn 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 the turn decides which spells to play and what those spells target, and makes any required decisions when those spells resolve.

Example: The controller of the turn decides which of the player’s creatures attack, and how those creatures assign their combat damage.

Example: The controller of the turn decides which card the player chooses from outside the game with one of the Judgment™ Wishes. The player can’t choose a card of the wrong type.