Destined Confrontation

Each player chooses any number of creatures they control with total power 4 or less, then sacrifices all other creatures they control.

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.

Razor Rings

Razor Rings deals 4 damage to target attacking or blocking creature. You gain life equal to the excess damage dealt this way.

White Lotus Reinforcements

Vigilance
Other Allies you control get +1/+1.

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.)

Saber-Tooth Moose-Lion

Reach
Forestcycling {2} ({2}, Discard this card: Search your library for a Forest card, reveal it, put it into your hand, then shuffle.)

Suki, Courageous Rescuer

Other creatures you control get +1/+0.
Whenever another permanent you control leaves the battlefield during your turn, create a 1/1 white Ally creature token. This ability triggers only once each turn.

Allies at Last

Affinity for Allies (This spell costs {1} less to cast for each Ally you control.)
Up to two target creatures you control each deal damage equal to their power to target creature an opponent controls.

Badgermole Cub

When this creature 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.)
Whenever you tap a creature for mana, add an additional {G}.

Plains

Enter the Avatar State

Until end of turn, target creature you control becomes an Avatar in addition to its other types and gains flying, first strike, lifelink, and hexproof. (A creature with hexproof can't be the target of spells or abilities your opponents control.)

The Boulder, Ready to Rumble

Whenever The Boulder attacks, earthbend X, where X is the number of creatures you control with power 4 or greater. (Target land you control becomes a 0/0 creature with haste that's still a land. Put X +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped.)

South Pole Voyager

Whenever this creature or another Ally you control enters, you gain 1 life. If this is the second time this ability has resolved this turn, draw a card.

Forest

Zuko's Exile

Exile target artifact, creature, or enchantment. Its controller creates a Clue token. (It's an artifact with "{2}, Sacrifice this token: Draw a card.")

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.)

Cycle of Renewal

Sacrifice a land. Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

True Ancestry

Return up to one target permanent card from your graveyard to your hand.
Create a Clue token. (It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Rebellious Captives

Exhaust — {6}: Put two +1/+1 counters on this creature, then 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. Activate each exhaust ability only once.)

Water Tribe Captain

{5}: Creatures you control get +1/+1 until end of turn.

Uncle Iroh

Firebending 1 (Whenever this creature attacks, add {R}. This mana lasts until end of combat.)
Lesson spells you cast cost {1} less to cast.

Avatar Enthusiasts

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

Momo, Playful Pet

Flying, vigilance
When Momo leaves the battlefield, choose one —
• Create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")
• Put a +1/+1 counter on target creature you control.
• Scry 2.

Rocky Rebuke

Target creature you control deals damage equal to its power to target creature an opponent controls.