Banding is a keyword ability which allows multiple creatures to attack as a group in combat, and which allows sharing of combat damage.

Technical Explanation

Banding is a static ability which modifies the rules of combat in two ways:

Mutual Assistance -- The first aspect of banding is the ability to attack with a group, sometimes referred to as "mutual assistance". When you declare your attackers, you may create "bands" of creatures which are all attacking the same player or planeswalker. A band consists of any number of creatures that have banding, plus up to one creature that does not. For example: a band could consist of one Benalish Hero , one Mesa Pegasus and one Runeclaw Bear . The band cannot contain two runeclaw bears.

Abilities are not shared between the creatures of the band. If one creature in the band becomes blocked, all of the creatures become blocked. For example, If an attacking band consists of a Mesa Pegasus and a Runeclaw Bear , the defending player can block the runeclaw with a Hill giant . Both the mesa pegasus and the runeclaw bear are now being blocked by the hill giant.

You do not declare bands when blocking, though banding is still useful for the damage sharing effect:

Damage Sharing -- The second aspect of banding is that combat damage can be distributed among your creatures however you choose. Normally, the player who's creatures are dealing the combat damage chooses how damage is distributed. If a creature with banding is among the creatures that might be dealt combat damage, the player who's creatures are being dealt the damage distributes damage. When doing so, the damage assignment order can be ignored. This reversal of who assigns combat damage also occurs if a blocking creature has banding.

Implications

• When a band becomes blocked, the blocking creature is now blocking multiple attackers. As a result, the defending player needs to announce a damage assignment order for his blocking creature. This order will probably be irrelevant since banding also modifies the rules for assigning damage, but if the creature with banding dies or loses banding it may matter.

• Once a band has been declared, the band exists for the rest of combat. If any or all the creatures lose banding, the band still exists, and blocking one creature will still cause the whole band to become blocked.

Special Forms

• Bands With Other [quality]. A creature with bands with other can form a band with any number of creatures that have the specified quality, even if those creatures don't have banding.

Interactions

• . . . with itself: multiple instances of banding on the same creature are redundant. Multiple instances of Bands With Other are redundant if they specify the same quality.

• . . . with abilities on creatures it is banded with: Banding does not cause creatures to share abilities. Each creature in a band has only its own abilities.

Comprehensive Rules

As of Magic 2013, the full official rules for this ability are as follows:

702.20. Banding

702.20a Banding is a static ability that modifies the rules for combat.

702.20b "Bands with other" is a special form of banding. If an effect causes a permanent to lose banding, the permanent loses all "bands with other" abilities as well.

702.20c As a player declares attackers, he or she may declare that one or more attacking creatures with banding and up to one attacking creature without banding (even if it has "bands with other") are all in a "band." He or she may also declare that one or more attacking [quality] creatures with "bands with other [quality]" and any number of other attacking [quality] creatures are all in a band. A player may declare as many attacking bands as he or she wants, but each creature may be a member of only one of them. (Defending players can't declare bands but may use banding in a different way; see rule 702.20j.)

702.20d All creatures in an attacking band must attack the same player or planeswalker.

702.20e Once an attacking band has been announced, it lasts for the rest of combat, even if something later removes banding or "bands with other" from one or more of the creatures in the band.

702.20f An attacking creature that's removed from combat is also removed from the band it was in.

702.20g Banding doesn't cause attacking creatures to share abilities, nor does it remove any abilities. The attacking creatures in a band are separate permanents.

702.20h If an attacking creature becomes blocked by a creature, each other creature in the same band as the attacking creature becomes blocked by that same blocking creature.Example: A player attacks with a band consisting of a creature with flying and a creature with swampwalk. The defending player, who controls a Swamp, can block the flying creature if able. If he or she does, then the creature with swampwalk will also become blocked by the blocking creature(s).

702.20i If one member of a band would become blocked due to an effect, the entire band becomes blocked.

702.20j During the combat damage step, if an attacking creature is being blocked by a creature with banding, or by both a [quality] creature with "bands with other [quality]" and another [quality] creature, the defending player (rather than the active player) chooses how the attacking creature's damage is assigned. That player can divide that creature's combat damage as he or she chooses among any number of creatures blocking it. This is an exception to the procedure described in rule 510.1c.

702.20k During the combat damage step, if a blocking creature is blocking a creature with banding, or both a [quality] creature with "bands with other [quality]" and another [quality] creature, the active player (rather than the defending player) chooses how the blocking creature's damage is assigned. That player can divide that creature's combat damage as he or she chooses among any number of creatures it's blocking. This is an exception to the procedure described in rule 510.1d.

702.20m Multiple instances of banding on the same creature are redundant. Multiple instances of "bands with other" of the same kind on the same creature are redundant.