Helm of Chatzuk

2008-10-01 A maximum of one nonbanding creature can join an attacking band no matter how many creatures with banding are in it.
2008-10-01 Creatures in the same band must all attack the same player or planeswalker.
2008-10-01 If a creature with banding attacks, it can team up with any number of other attacking creatures with banding (and up to one nonbanding creature) and attack as a unit called a "band." The band can be blocked by any creature that could block a single creature in the band. Blocking any creature in a band blocks the entire band. If a creature with banding is blocked, the attacking player chooses how the blockers' damage is assigned.
2009-10-01 If a creature in combat has banding, its controller assigns damage for creatures blocking or blocked by it. That player can ignore the damage assignment order when making this assignment.

mtg.wtf