Formation
Formation 

Draw a card at the beginning of the next turn's upkeep.
"I have been a warrior for over four hundred years, and yet each generation of Kjeldorans teaches me new tricks. There can be no better allies." —Taaveti of Kelsinko, Elvish Hunter
Legality
Rulings
2009-10-01
If a creature in combat has banding, its controller assigns damage for creatures blocking or blocked by it.
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.
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.