Yue, the Moon Spirit

Flying, vigilance
Waterbend {5}, {T}: You may cast a noncreature spell from your hand without paying its mana cost.

Watery Grasp

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.
Waterbend {5}: Enchanted creature's owner shuffles it into their library. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)

Sokka, Wolf Cove's Protector

Vigilance (Attacking doesn't cause this creature to tap.)

Earthbending Lesson

Earthbend 4. (Target land you control becomes a 0/0 creature with haste that's still a land. Put four +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped.)

Aang, Air Nomad

Flying (This creature can't be blocked except by creatures with flying or reach.)
Vigilance (Attacking doesn't cause this creature to tap.)
Other creatures you control have vigilance.

Hada Freeblade

Whenever this creature or another Ally you control enters, you may put a +1/+1 counter on this creature.

Aang, Airbending Master

When Aang enters, airbend another target creature. (Exile it. While it's exiled, its owner may cast it for {2} rather than its mana cost.)
Whenever one or more creatures you control leave the battlefield without dying, you get an experience counter.
At the beginning of your upkeep, create a 1/1 white Ally creature token for each experience counter you have.

Umara Raptor

Flying
Whenever this creature or another Ally you control enters, you may put a +1/+1 counter on this creature.

Veteran Warleader

Veteran Warleader's power and toughness are each equal to the number of creatures you control.
Tap another untapped Ally you control: This creature gains your choice of first strike, vigilance, or trample until end of turn.

Talus Paladin

Whenever this creature or another Ally you control enters, you may have Allies you control gain lifelink until end of turn, and you may put a +1/+1 counter on this creature.

It'll Quench Ya!

Counter target spell unless its controller pays {2}.

Haru, Hidden Talent

Whenever another Ally you control enters, earthbend 1. (Target land you control becomes a 0/0 creature with haste that's still a land. Put a +1/+1 counter on it. When it dies or is exiled, return it to the battlefield tapped.)

Katara, Water Tribe's Hope

Vigilance
When Katara enters, create a 1/1 white Ally creature token.
Waterbend {X}: Creatures you control have base power and toughness X/X until end of turn. X can't be 0. Activate only during your turn. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)

Earth Rumble

Earthbend 2. When you do, up to one target creature you control fights target creature an opponent controls. (To earthbend 2, target land you control becomes a 0/0 creature with haste that's still a land. Put two +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped. Creatures that fight each deal damage equal to their power to the other.)

Kyoshi Warrior Guard

Sokka, Lateral Strategist

Vigilance
Whenever Sokka and at least one other creature attack, draw a card.

Jeong Jeong's Deserters

When this creature enters, put a +1/+1 counter on target creature.

Master Piandao

First strike
Whenever Master Piandao attacks, look at the top four cards of your library. You may reveal an Ally, Equipment, or Lesson card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Match the Odds

Create a 1/1 white Ally creature token. Put a +1/+1 counter on it for each creature your opponents control.

Spawnbinder Mage

Cohort — {T}, Tap an untapped Ally you control: Tap target creature.

Avatar Enthusiasts

Whenever another Ally you control enters, put a +1/+1 counter on this creature.

Sea Gate Loremaster

{T}: Draw a card for each Ally you control.

Harabaz Druid

{T}: Add X mana of any one color, where X is the number of Allies you control.

Flexible Waterbender

Vigilance
Waterbend {3}: This creature has base power and toughness 5/2 until end of turn. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)

Water Whip

As an additional cost to cast this spell, waterbend {5}. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)
Return up to two target creatures to their owners' hands. Draw two cards.

Vastwood Animist

{T}: Target land you control becomes an X/X Elemental creature until end of turn, where X is the number of Allies you control. It's still a land.

Earthbending Student

When this creature enters, earthbend 2. (Target land you control becomes a 0/0 creature with haste that's still a land. Put two +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped.)
Land creatures you control have vigilance. (Attacking doesn't cause them to tap.)

Seismic Tutelage

Enchant creature
When this Aura enters, put a +1/+1 counter on enchanted creature.
Whenever enchanted creature attacks, double the number of +1/+1 counters on it.

Island

Kabira Evangel

Whenever this creature or another Ally you control enters, you may choose a color. If you do, Allies you control gain protection from the chosen color until end of turn.

Relief Captain

When this creature enters, support 3. (Put a +1/+1 counter on each of up to three other target creatures.)

Glider Kids

Flying
When this creature enters, scry 1. (Look at the top card of your library. You may put it on the bottom.)

Tajuru Beastmaster

Rally — Whenever this creature or another Ally you control enters, creatures you control get +1/+1 until end of turn.

Oran-Rief Survivalist

Allied Teamwork

When this enchantment enters, create a 1/1 white Ally creature token.
Allies you control get +1/+1.

Sylvan Advocate

Vigilance
As long as you control six or more lands, this creature and land creatures you control get +2/+2.

Katara, Bending Prodigy

At the beginning of your end step, if Katara is tapped, put a +1/+1 counter on her.
Waterbend {6}: Draw a card. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)

Plains

Aang, the Last Airbender

Flying
When Aang enters, airbend up to one other target nonland permanent. (Exile it. While it's exiled, its owner may cast it for {2} rather than its mana cost.)
Whenever you cast a Lesson spell, Aang gains lifelink until end of turn.

Suki, Kyoshi Warrior

Suki's power is equal to the number of creatures you control.
Whenever Suki attacks, create a 1/1 white Ally creature token that's tapped and attacking.

Munda's Vanguard

Cohort — {T}, Tap an untapped Ally you control: Put a +1/+1 counter on each creature you control.

Turtle-Duck

{3}: Until end of turn, this creature has base power 4 and gains trample.

Toph, the Blind Bandit

When Toph enters, earthbend 2. (Target land you control becomes a 0/0 creature with haste that's still a land. Put two +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped.)
Toph's power is equal to the number of +1/+1 counters on lands you control.

Katara, Waterbending Master

Whenever you cast a spell during an opponent's turn, you get an experience counter.
Whenever Katara attacks, you may draw a card for each experience counter you have. If you do, discard a card.

Graypelt Hunter

Trample
Whenever this creature or another Ally you control enters, you may put a +1/+1 counter on this creature.

Airbending Lesson

Airbend target nonland permanent. (Exile it. While it's exiled, its owner may cast it for {2} rather than its mana cost.)
Draw a card.

Katara, the Fearless

If a triggered ability of an Ally you control triggers, that ability triggers an additional time.

Sokka's Haiku

Counter target spell.
Draw a card, then mill three cards.
Untap target land.

Jwari Shapeshifter

You may have this creature enter as a copy of any Ally creature on the battlefield.

Master Pakku

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Master Pakku becomes tapped, target player mills X cards, where X is the number of Lesson cards in your graveyard. (They put the top X cards of their library into their graveyard.)

Waterbending Lesson

Draw three cards. Then discard a card unless you waterbend {2}. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)

Kazandu Blademaster

First strike, vigilance
Whenever this creature or another Ally you control enters, you may put a +1/+1 counter on this creature.

Katara, Heroic Healer

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
When Katara enters, put a +1/+1 counter on each other creature you control.