308.2a The active player either chooses to not attack, or chooses one or more creatures he or she controls and then determines whether this set of creatures could attack. Only creatures can attack, and the following creatures can’t attack: tapped creatures (even those that can attack without tapping) and creatures the active player didn’t control continuously since the beginning of the turn (except those with haste). Other effects may also affect whether or not a set of creatures could attack. (See rule 500, “Legal Attacks and Blocks.”)

308.2b If any of the chosen creatures have banding or a bands with other ability, the active player announces which creatures, if any, are banded with which. (See rule 502.10, “Banding.”)

308.2c The active player taps the chosen creatures. Tapping a creature when it’s declared as an attacker isn’t a cost; attacking simply causes creatures to become tapped.

308.2d If any of the creatures require paying costs to attack, the active player determines the total cost to attack. 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.

308.2e If any of the costs require mana, the active player then has a chance to play mana abilities (see rule 411, “Playing Mana Abilities”).

308.2f 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.

308.2g Each chosen creature becomes an attacking creature if all costs have been paid, but only if it’s still controlled by the active player. It remains an attacking creature until it’s removed from combat or the combat phase ends, whichever comes first. See rule 306.2.

308.3. Abilities that trigger on a creature attacking trigger only at the point the creature is declared as an attacker. They will not trigger if a creature attacks and then that creature’s characteristics change to match the ability’s trigger condition. They will not trigger if a creature is put into play attacking.

Example: A permanent has the ability “Whenever a green creature attacks, destroy that creature at end of combat.” If a blue creature attacks and is later turned green, the ability will not trigger.

308.4. If no creatures are declared as attackers, finish the declare attackers step, but skip the declare blockers and combat damage steps.

309.1. As the declare blockers step begins, the defending player declares blockers (this game action doesn’t use the stack). Then any abilities that triggered on blockers being declared go on the stack. (See rule 410, “Handling Triggered Abilities.”) Then the active player gets priority and players may play spells and abilities.

309.2. 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 422, “Handling Illegal Actions,” and rule 500, “Legal Attacks and Blocks”).

309.2a The defending player chooses zero or more creatures he or she controls, chooses one attacking creature for each one to block, then determines whether this set of blocks is legal. Only untapped creatures can block, but blocking does not cause creatures to tap. Other effects may also affect whether or not a set of creatures could block. (See rule 500, “Legal Attacks and Blocks.”)

309.2b If any of the 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.

309.2c If any of the costs require mana, the defending player then has a chance to play mana abilities (see rule 411, “Playing Mana Abilities”).

309.2d 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.

309.2e Each chosen creature becomes a blocking creature, but only if it’s controlled by the defending player. Each one is blocking the attacking creature chosen for it. It remains a blocking creature until it’s removed from combat or the combat phase ends, whichever comes first. See rule 306.2.

309.2f An attacking creature with one or more creatures declared as blockers for it becomes a blocked creature; one with no blockers becomes an unblocked creature. This remains unchanged until the creature is removed from combat or the combat phase ends, whichever comes first. (Some effects can change whether a creature is blocked or unblocked.)

309.3. Abilities that trigger on a creature blocking trigger only at the point the creature is declared as a blocker. They will not trigger if a creature blocks, and then that creature’s characteristics change to match the ability’s trigger condition. They will not trigger if a creature is put into play blocking.

309.4. Abilities that trigger on a creature becoming blocked trigger only at the first point the creature becomes blocked that combat. They will trigger if a creature becomes blocked by a creature declared as a blocker, by a creature that’s put into play as a blocker, or by an effect, but only if the attacking creature hadn’t yet been blocked that combat. They will not trigger if a creature becomes blocked, and then the blocking creature’s characteristics change to match the ability’s trigger condition.

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

310.1. As the combat damage step begins, the active player announces how each attacking creature will assign its combat damage. Then the defending player announces how each blocking creature will assign its combat damage. All assignments of combat damage go on the stack as a single object. Then any abilities that triggered on damage being assigned go on the stack. (See rule 410, “Handling Triggered Abilities.”) Then the active player gets priority and players may play spells and abilities.

310.2. A player may divide a creature’s combat damage as he or she chooses among the legal recipients. Dividing combat damage is subject to the following restrictions:

310.2a Each attacking creature and each blocking creature will assign combat damage equal to its power. Creatures with 0 or less power don’t assign combat damage.

310.2b An unblocked attacking creature will assign all its combat damage to the defending player.