510.1.
First, the active player announces how each attacking creature assigns its combat damage, then
the defending player announces how each blocking creature assigns its combat damage. This turnbased
action doesn‘t use the stack. A player assigns a creature‘s combat damage according to the
following rules:
510.1a
Each attacking creature and each blocking creature assigns combat damage equal to its
power. Creatures that would assign 0 or less damage this way don‘t assign combat damage at
all.
510.1b
An unblocked creature assigns its combat damage to the player or planeswalker it‘s
attacking. If it isn‘t currently attacking anything (if, for example, it was attacking a planeswalker
that has left the battlefield), it assigns no combat damage.
510.1c
A blocked creature assigns its combat damage to the creatures blocking it. If no creatures are
currently blocking it (if, for example, they were destroyed or removed from combat), it assigns
no combat damage. If exactly one creature is blocking it, it assigns all its combat damage to that
creature. If two or more creatures are blocking it, it assigns its combat damage to those creatures
according to the damage assignment order announced for it. This may allow the blocked
creature to divide its combat damage. However, it can‘t assign combat damage to a creature
that‘s blocking it unless, when combat damage assignments are complete, each creature that
precedes that blocking creature in its order is assigned lethal damage. When checking for
assigned lethal damage, take into account damage already marked on the creature and damage
from other creatures that‘s being assigned during the same combat damage step, but not any
abilities or effects that might change the amount of damage that‘s actually dealt. An amount of
damage that‘s greater than a creature‘s lethal damage may be assigned to it.
Example: The damage assignment order of an attacking Vastwood Gorger (a 5/6
creature) is Pride Guardian (a 0/3 creature) then Llanowar Elves (a 1/1 creature).
Vastwood Gorger can assign 3 damage to the Guardian and 2 damage to the Elves, 4
damage to the Guardian and 1 damage to the Elves, or 5 damage to the Guardian.
Example: The damage assignment order of an attacking Vastwood Gorger (a 5/6
creature) is Pride Guardian (a 0/3 creature) then Llanowar Elves (a 1/1 creature).
During the declare blockers step, the defending player casts Giant Growth targeting
Pride Guardian, which gives it +3/+3 until end of turn. Vastwood Gorger must assign
its 5 damage to the Guardian.
Example: The damage assignment order of an attacking Vastwood Gorger (a 5/6
creature) is Pride Guardian (a 0/3 creature) then Llanowar Elves (a 1/1 creature).
During the declare blockers step, the defending player casts Mending Hands targeting
Pride Guardian, which prevents the next 4 damage that would be dealt to it. Vastwood
Gorger can assign 3 damage to the Guardian and 2 damage to the Elves, 4 damage to
the Guardian and 1 damage to the Elves, or 5 damage to the Guardian.
Example: The damage assignment order of an attacking Enormous Baloth (a 7/7
creature) is Trained Armodon (a 3/3 creature) that already has 2 damage marked on it,
then Foriysian Brigade (a 2/4 creature that can block an additional creature), then
Silverback Ape (a 5/5 creature). The damage assignment order of an attacking
Durkwood Boars (a 4/4 creature) is the same Foriysian Brigade, then Goblin Piker (a
2/1 creature). Among other possibilities, the active player may have the Baloth assign 1
damage to the Armodon, 1 damage to the Brigade, and 5 damage to the Ape, and have
the Boars assign 3 damage to the Brigade and 1 damage to the Piker.
510.1d
A blocking creature assigns combat damage to the creatures it‘s blocking. If it isn‘t currently
blocking any creatures (if, for example, they were destroyed or removed from combat), it
assigns no combat damage. If it‘s blocking exactly one creature, it assigns all its combat damage
to that creature. If it‘s blocking two or more creatures, it assigns its combat damage to those
creatures according to the damage assignment order announced for it. This may allow the
blocking creature to divide its combat damage. However, it can‘t assign combat damage to a
creature that it‘s blocking unless, when combat damage assignments are complete, each creature
that precedes that blocked creature is assigned lethal damage. When checking for assigned lethal
damage, take into account damage already marked on the creature and damage from other
creatures that‘s being assigned during the same combat damage step, but not any abilities or
effects that might change the amount of damage that‘s actually dealt. An amount of damage
that‘s greater than a creature‘s lethal damage may be assigned to it.
510.1e
Once a player has assigned combat damage from each attacking or blocking creature he or
she controls, the total damage assignment (not solely the damage assignment of any individual
attacking or blocking creature) is checked to see if it complies with the above rules. If it doesn‘t,
the combat damage assignment is illegal; the game returns to the moment before that player
began to assign combat damage. (See rule 717, «Handling Illegal Actions»).
510.2.
Second, all combat damage that‘s been assigned is dealt simultaneously. This turn-based action
doesn‘t use the stack. No player has the chance to cast spells or activate abilities between the time
combat damage is assigned and the time it‘s dealt. This is a change from previous rules.
Example: Squadron Hawk (a 1/1 creature with flying) and Goblin Piker (a 2/1 creature) are
attacking. Mogg Fanatic (a 1/1 creature with the ability “Sacrifice Mogg Fanatic: Mogg
Fanatic deals 1 damage to target creature or player) blocks the Goblin Piker. The defending
player sacrifices Mogg Fanatic during the declare blockers step to deal 1 damage to the
Squadron Hawk. The Hawk is destroyed. The Piker deals and is dealt no combat damage
this turn. If the defending player instead left Mogg Fanatic on the battlefield, the Fanatic
and the Piker would have dealt lethal damage to one another, but the Squadron Hawk
couldn?t have been dealt damage.
510.3.
Third, any abilities that triggered on damage being assigned or dealt go on the stack. (See rule
603, «Handling Triggered Abilities.»)
510.4.
Fourth, the active player gets priority. Players may cast spells and activate abilities.
510.5.
If at least one attacking or blocking creature has first strike (see rule 702.7) or double strike (see
rule 702.4) as the combat damage step begins, the only creatures that assign combat damage in that
step are those with first strike or double strike. After that step, instead of proceeding to the end of
combat step, the phase gets a second combat damage step. The only creatures that assign combat
damage in that step are the remaining attackers and blockers that had neither first strike nor double
strike as the first combat damage step began, as well as the remaining attackers and blockers that
currently have double strike. After that step, the phase proceeds to the end of combat step.