Sokka and Suki

Whenever Sokka and Suki or another Ally you control enters, attach up to one target Equipment you control to that creature.
Whenever an Equipment you control enters, create a 1/1 white Ally creature token.

Aang and Katara

Whenever Aang and Katara enter or attack, create X 1/1 white Ally creature tokens, where X is the number of tapped artifacts and/or creatures you control.

Earthshape

Earthbend 3. Then each creature you control with power less than or equal to that land's power gains hexproof and indestructible until end of turn. You gain hexproof until end of turn.

Toph, Greatest Earthbender

When Toph enters, earthbend X, where X is the amount of mana spent to cast her.
Land creatures you control have double strike.

Mai and Zuko

Firebending 3
You may cast Ally spells and artifact spells as though they had flash.

Swampbenders

Swampbenders's power and toughness are each equal to the number of Swamps on the battlefield.
Lands you control are Swamps in addition to their other types.

Fire Nation Turret

At the beginning of combat on your turn, up to one target creature gets +2/+0 and gains firebending 2 until end of turn.
{R}: Put a charge counter on this artifact.
Remove fifty charge counters from this artifact: It deals 50 damage to any target.

Appa, the Vigilant

Flying, vigilance
Whenever Appa or another Ally you control enters, creatures you control get +1/+1 and gain flying and vigilance until end of turn.

Uncle's Musings

Converge — Return up to X permanent cards from your graveyard to your hand, where X is the number of colors of mana spent to cast this spell.
Exile Uncle's Musings.

Katara's Reversal

Counter up to four target spells and/or abilities.
Untap up to four target artifacts and/or creatures.

Sokka's Charge

During your turn, Allies you control have double strike and lifelink.

Momo's Heist

Gain control of target artifact. Untap it. It gains haste. At the beginning of the next end step, sacrifice it.