Declare blockers step

The declare blockers step is a step of the combat phase, where attacking creatures may be blocked.

Creatures assigned in this step are blocking.

Blocking mechanics

Blocking extra creatures

By default, each blocking creature can only block one attacking creature. Some creatures have a mechanic that allows them to block extra creatures (This creature can block an additional N creatures each combat.). This mechanic used to be primary in white and green. This is an ability that R&D have stopped using for various reasons.

Can't be blocked

Can't be blocked (AKA Unblockable) is primary in blue.

Can’t be blocked by creatures with power 2 or less

This ability, nicknamed Daunt, appears irregularly green.

Can't block

The "Can't block" drawback is primary in black and secondary in red.

Deals damage when blocked

This effect is done primarily in red creatures. When black does it, it is usually loss of life. Afflict also does this in blue.

Forced block

Forced block (Target creature must block this turn.) is seldom used but primary in red and secondary in green.

Rules

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

Declare Blockers Step

Part of the turn. This step is the third step of the combat phase. See rule 509, “Declare Blockers Step.”

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

• 509. Declare Blockers Step
  • 509.1. First, the defending player declares blockers. This turn-based action doesn’t use the stack. To declare blockers, the defending player follows the steps below, in order. If at any point during the declaration of blockers, the defending player is unable to comply with any of the steps listed below, the declaration is illegal; the game returns to the moment before the declaration (see rule 730, “Handling Illegal Actions”).
    • 509.1a The defending player chooses which creatures they control, if any, will block. The chosen creatures must be untapped and they can’t also be battles. For each of the chosen creatures, the defending player chooses one creature for it to block that’s attacking that player, a planeswalker they control, or a battle they protect.
    • 509.1b The defending player checks each creature they control to see whether it’s affected by any restrictions (effects that say a creature can’t block, or that it can’t block unless some condition is met). If any restrictions are being disobeyed, the declaration of blockers is illegal.
      A restriction may be created by an evasion ability (a static ability an attacking creature has that restricts what can block it). If an attacking creature gains or loses an evasion ability after a legal block has been declared, it doesn’t affect that block. Different evasion abilities are cumulative.

      Example: An attacking creature with flying and shadow can’t be blocked by a creature with flying but without shadow.

    • 509.1c The defending player checks each creature they control to see whether it’s affected by any requirements (effects that say a creature must block, or that it must block if some condition is met). If the number of requirements that are being obeyed is fewer than the maximum possible number of requirements that could be obeyed without disobeying any restrictions, the declaration of blockers is illegal. If a creature can’t block unless a player pays a cost, that player is not required to pay that cost, even if blocking with that creature would increase the number of requirements being obeyed. If a requirement that says a creature blocks if able during a certain turn refers to a turn with multiple combat phases, the creature blocks if able during each declare blockers step in that turn.

      Example: A player controls one creature that “blocks if able” and another creature with no abilities. If a creature with menace attacks that player, the player must block with both creatures. Having only the first creature block violates the restriction created by menace (the attacking creature can’t be blocked except by two or more creatures). Having only the second creature block violates both the menace restriction and the first creature’s blocking requirement. Having neither creature block fulfills the restriction but not the requirement.

    • 509.1d If any of the chosen creatures require paying costs to block, the defending player determines the total cost to block. Costs may include paying mana, tapping permanents, sacrificing permanents, discarding cards, and so on. Once the total cost is determined, it becomes “locked in.” If effects would change the total cost after this time, ignore this change.
    • 509.1e If any of the costs require mana, the defending player then has a chance to activate mana abilities (see rule 605, “Mana Abilities”).
    • 509.1f Once the player has enough mana in their mana pool, they pay all costs in any order. Partial payments are not allowed.
    • 509.1g Each chosen creature still controlled by the defending player becomes a blocking creature. Each one is blocking the attacking creatures chosen for it. It remains a blocking creature until it’s removed from combat or the combat phase ends, whichever comes first. See rule 506.4.
    • 509.1h An attacking creature with one or more creatures declared as blockers for it becomes a blocked creature; one with no creatures declared as blockers for it becomes an unblocked creature. This remains unchanged until the creature is removed from combat, an effect says that it becomes blocked or unblocked, or the combat phase ends, whichever comes first. A creature remains blocked even if all the creatures blocking it are removed from combat.
    • 509.1i Any abilities that trigger on blockers being declared trigger. See rule 509.4 for more information.
  • 509.2. Second, for each attacking creature that’s become blocked, the active player announces that creature’s damage assignment order, which consists of the creatures blocking it in an order of that player’s choice. (During the combat damage step, an attacking creature can’t assign combat damage to a creature that’s blocking it unless each creature ahead of that blocking creature in its order is assigned lethal damage.) This turn-based action doesn’t use the stack.

    Example: Vastwood Gorger is blocked by Llanowar Elves, Runeclaw Bear, and Serra Angel. Vastwood Gorger’s controller announces the Vastwood Gorger’s damage assignment order as Serra Angel, then Llanowar Elves, then Runeclaw Bear.

    • 509.2a During the declare blockers step, if a blocking creature is removed from combat or a spell or ability causes it to stop blocking an attacking creature, the blocking creature is removed from all relevant damage assignment orders. The relative order among the remaining blocking creatures is unchanged.
  • 509.3. Third, for each blocking creature, the defending player announces that creature’s damage assignment order, which consists of the creatures it’s blocking in an order of that player’s choice. (During the combat damage step, a blocking creature can’t assign combat damage to a creature it’s blocking unless each creature ahead of that blocked creature in its order is assigned lethal damage.) This turn-based action doesn’t use the stack.
    • 509.3a During the declare blockers step, if an attacking creature is removed from combat or a spell or ability causes it to stop being blocked by a blocking creature, the attacking creature is removed from all relevant damage assignment orders. The relative order among the remaining attacking creatures is unchanged.
  • 509.4. Fourth, the active player gets priority. (See rule 117, “Timing and Priority.”)
    • 509.4a Any abilities that triggered on blockers being declared or that triggered during the process described in rules 509.1–3 are put onto the stack before the active player gets priority; the order in which they triggered doesn’t matter. (See rule 603, “Handling Triggered Abilities.”)
  • 509.5. Triggered abilities that trigger on blockers being declared may have different trigger conditions.
    • 509.5a An ability that reads “Whenever [a creature] blocks, . . .” generally triggers only once each combat for that creature, even if it blocks multiple creatures. It triggers if the creature is declared as a blocker. It will also trigger if that creature becomes a blocker as the result of an effect, but only if it wasn’t a blocking creature at that time. (See rule 509.1g.) It won’t trigger if the creature is put onto the battlefield blocking.
    • 509.5b An ability that reads “Whenever [a creature] blocks a creature, . . .” triggers once for each attacking creature the creature with the ability blocks. It triggers if the creature is declared as a blocker. It will also trigger if an effect causes that creature to block an attacking creature, but only if it wasn’t already blocking that attacking creature at that time. It won’t trigger if the creature is put onto the battlefield blocking.
    • 509.5c An ability that reads “Whenever [a creature] becomes blocked, . . .” generally triggers only once each combat for that creature, even if it’s blocked by multiple creatures. It will trigger if that creature becomes blocked by at least one creature declared as a blocker. It will also trigger if that creature becomes blocked by an effect or by a creature that’s put onto the battlefield as a blocker, but only if the attacking creature was an unblocked creature at that time. (See rule 509.1h.)
    • 509.5d An ability that reads “Whenever [a creature] becomes blocked by a creature, . . .” triggers once for each creature that blocks the specified creature. It triggers if a creature is declared as a blocker for the attacking creature. It will also trigger if an effect causes a creature to block the attacking creature, but only if it wasn’t already blocking that attacking creature at that time. In addition, it will trigger if a creature is put onto the battlefield blocking that creature. It won’t trigger if the creature becomes blocked by an effect rather than a creature.
    • 509.5e If an ability triggers when a creature blocks or becomes blocked by a particular number of creatures, the ability triggers if the creature blocks or is blocked by that many creatures when blockers are declared. Effects that add or remove blockers can also cause such abilities to trigger. This applies to abilities that trigger on a creature blocking or being blocked by at least a certain number of creatures as well.
    • 509.5f If an ability triggers when a creature with certain characteristics blocks, it will trigger only if the creature has those characteristics at the point blockers are declared, or at the point an effect causes it to block. If an ability triggers when a creature with certain characteristics becomes blocked, it will trigger only if the creature has those characteristics at the point it becomes a blocked creature. If an ability triggers when a creature becomes blocked by a creature with certain characteristics, it will trigger only if the latter creature has those characteristics at the point it becomes a blocking creature. None of those abilities will trigger if the relevant creature’s characteristics change to match the ability’s trigger condition later on.

      Example: A creature has the ability “Whenever this creature becomes blocked by a white creature, destroy that creature at end of combat.” If the creature becomes blocked by a black creature that is later turned white, the ability will not trigger.

    • 509.5g An ability that reads “Whenever [a creature] attacks and isn’t blocked, . . .” triggers if no creatures are declared as blockers for that creature. It will trigger even if the creature was never declared as an attacker (for example, if it entered the battlefield attacking). It won’t trigger if the attacking creature is blocked and then all its blockers are removed from combat.
  • 509.6. If a spell or ability causes a creature on the battlefield to block an attacking creature, the active player announces the blocking creature’s placement in the attacking creature’s damage assignment order. The relative order among the remaining blocking creatures is unchanged. Then the defending player announces the attacking creature’s placement in the blocking creature’s damage assignment order. The relative order among the remaining attacking creatures is unchanged. This is done as part of the blocking effect.
  • 509.7. If a creature is put onto the battlefield blocking, its controller chooses which attacking creature it’s blocking as it enters the battlefield (unless the effect that put it onto the battlefield specifies what it’s blocking), then the active player announces the new creature’s placement in the blocked creature’s damage assignment order. The relative order among the remaining blocking creatures is unchanged. A creature put onto the battlefield this way is “blocking” but, for the purposes of trigger events and effects, it never “blocked.”

    Example: Giant Spider is blocked by Canyon Minotaur. The defending player casts Flash Foliage, which creates a Saproling creature token blocking the Giant Spider. Giant Spider’s controller announces the Giant Spider’s damage assignment order as the Saproling token, then Canyon Minotaur.

    • 509.7a If the effect that puts a creature onto the battlefield blocking specifies it’s blocking a certain creature and that creature is no longer attacking, the creature is put onto the battlefield but is never considered a blocking creature. The same is true if the controller of the creature that’s put onto the battlefield blocking isn’t a defending player for the specified attacking creature.
    • 509.7b A creature that’s put onto the battlefield blocking isn’t affected by requirements or restrictions that apply to the declaration of blockers.