General Rulings - 509

• 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 was illegal; the game returns to the moment before the declaration (see Rule 714, "Handling Illegal Actions"). [CompRules 2009/07/08]
• 509.1a - The defending player chooses which creatures that he or she controls, if any, will block. The chosen creatures must be untapped. For each of the chosen creatures, the defending player chooses one creature for it to block that's attacking him, her, or a planeswalker he or she controls. [CompRules 2009/07/08]
• 509.1b - The defending player checks each creature he or she controls 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. [CompRules 2009/07/08]
  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. [CompRules 2009/07/08]
  Example: An attacking creature with flying and shadow can't be blocked by a creature with flying but without shadow. [CompRules 2009/07/08]
• 509.1c - The defending player checks each creature he or she controls 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. Tapped creatures and creatures with unpaid costs to block are exempt from effects that would require them to block. [CompRules 2009/07/08]
  Example: A player controls one creature that "blocks if able" and another creature with no abilities. An effect states, "Creatures can't be blocked except by two or more creatures." Having only the first creature block violates the restriction. Having neither creature block fulfills the restriction but not the requirement. Having both creatures block the same attacking creature fulfills both the restriction and the requirement, so that's the only option. [CompRules 2009/07/08]
• 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. [CompRules 2009/07/08]
• 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"). [CompRules 2009/07/08]
• 509.1f - Once the player has enough mana in his or her mana pool, he or she pays all costs in any order. Partial payments are not allowed. [CompRules 2009/07/08]
• 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. [CompRules 2009/10/01]
• 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. [CompRules 2009/10/01]
• 509.2 - Second, for each attacking creature that's become blocked by multiple creatures, the active player announces its damage assignment order among the blocking creatures. This turn-based action doesn't use the stack. (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.) [CompRules 2009/07/08]
  Example: Craw Wurm is blocked by Llanowar Elves, Runeclaw Bear, and Serra Angel. The Craw Wurm's controller announces the Craw Wurm's damage assignment order as Serra Angel, then Runeclaw Bear, then Llanowar Elves. [CompRules 2009/10/01]
• 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. [CompRules 2009/10/01]
• 509.3 - Third, for each creature that's blocking multiple creatures (because some effect allows it to), the defending player announces its damage assignment order among the attacking creatures. This turn-based action doesn't use the stack. (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.) [CompRules 2009/07/08]
• 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. [CompRules 2009/10/01]
• 509.4 - Fourth, any abilities that triggered on blockers being declared go on the stack. (See Rule 603, "Handling Triggered Abilities.") [CompRules 2009/07/08]
• 509.4a - An ability that reads "Whenever <-this 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.) [CompRules 2009/07/08]
• 509.4b - An ability that reads "Whenever <-this creature-> blocks a creature, ..." triggers once for each attacking creature the creature with the ability blocks. It triggers only if the creature is declared as a blocker. [CompRules 2009/07/08]
• 509.4c - An ability that reads "Whenever <-this 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.) [CompRules 2009/07/08]
• 509.4d - An ability that reads "Whenever <-this creature-> becomes blocked by a creature, ..." triggers once for each creature that blocks the named creature. It will also trigger if an effect causes a creature to block the attacking creature, even if it had already been blocked that combat. It won't trigger if the creature becomes blocked by an effect rather than a creature. [CompRules 2009/10/01]
• 509.4e - 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. [CompRules 2009/07/08]
• 509.4f - 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. 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 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. [CompRules 2009/07/08]
  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. [CompRules 2009/07/08]
• 509.4g - An ability that reads "Whenever <-this creature-> attacks and isn't blocked, ..." triggers if no creatures are declared as blockers for that creature. It won't trigger if the attacking creature is blocked and then all its blockers are removed from combat. [CompRules 2009/07/08]
• 509.5. - Fifth, the active player gets priority. Players may cast spells and activate abilities. [CompRules 2009/07/08]
• 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. [CompRules 2009/10/01]
• 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." [CompRules 2009/07/08]
  Example: Lumengrid Warden is blocked by Runeclaw Bear. The defending player casts Flash Foliage, which puts a Saproling token onto the battlefield blocking the Lumengrid Warden. Lumengrid Warden's controller announces the Lumengrid Warden's damage assignment order as the Saproling token, then Runeclaw Bear. [CompRules 2009/10/01]