802.1
Some multiplayer games allow the active player to attack multiple other players. If this option is used, a player can also choose to attack only one player during a particular combat.
Historical Rules · Effective 23 April 2010
Section 802: Attack Multiple Players Option
Read Section 802 continuously, or open any rule on its dedicated page.
Chapter 8 · Multiplayer Rules
Section 802
802. Attack Multiple Players Option
11 rules
802.2
As the combat phase starts, the attacking player doesn't choose an opponent to become the defending player. Instead, all the attacking player's opponents are defending players during the combat phase.
802.2a
Any rule, object, or effect that refers to a "defending player" refers to one specific defending player, not to all of the defending players. If the source of an ability that refers to a defending player is an attacking creature, it will usually refer to the player it's attacking or the controller of the planeswalker it's attacking. Similarly, if a spell or ability refers to both an attacking creature and a defending player, unless otherwise specified, the defending player it's referring to is the player that creature is attacking or the controller of the planeswalker it's attacking. If the spell or ability could apply to multiple attacking creatures, the appropriate defending player is individually determined for each of those attacking creatures. If there are multiple defending players that could be chosen, the controller of the spell or ability chooses one. Example: Rob attacks Alex with Runeclaw Bear and attacks Carissa with a creature with mountainwalk. Whether the creature with mountainwalk is unblockable depends only on whether Carissa controls a Mountain.
802.3
As the attacking player declares each attacking creature, he or she chooses a defending player or a planeswalker controlled by a defending player for it to attack. See rule 508, "Declare Attackers Step."
802.3a
Restrictions and requirements that don't apply to attacking a specific player are evaluated based on the entire group of attacking creatures. Restrictions and requirements that apply to attacking a specific player apply only to creatures attacking that player. The entire group of attacking creatures must still be legal. See rule 508.1.
802.3b
Creatures in a band can't attack different players. See rule 702.19, "Banding."
802.4
If more than one player is being attacked or controls a planeswalker that's being attacked, each defending player in APNAP order declares blockers as the declare blockers step begins. (See rule 101.4 and rule 509, "Declare Blockers Step.") The first defending player declares all his or her blocks, then the second defending player, and so on.
802.4a
A defending player can block only with creatures he or she controls. Those creatures can block only creatures attacking that player or a planeswalker that player controls.
802.4b
When determining whether a defending player's blocks are legal, ignore any creatures attacking other players and any blocking creatures controlled by other players.
802.5
After blockers have been declared, if any creatures are blocking multiple creatures, each defending player in APNAP order announces the damage assignment order among the attacking creatures for each blocking creature he or she controls. See rule 510, "Combat Damage Step."
802.6
Combat damage is assigned in APNAP order. Other than that, the combat damage step proceeds just as in a two-player game. See rule 510, "Combat Damage Step."