Longshot, Rebel Bowman

Reach (This creature can block creatures with flying.)
Noncreature spells you cast cost {1} less to cast.
Whenever you cast a noncreature spell, Longshot deals 2 damage to each opponent.

Zuko, Avatar Hunter

Reach (This creature can block creatures with flying.)
Whenever you cast a red spell, create a 2/2 red Soldier creature token.

It'll Quench Ya!

Counter target spell unless its controller pays {2}.

Sokka, Bold Boomeranger

When Sokka enters, discard up to two cards, then draw that many cards.
Whenever you cast an artifact or Lesson spell, put a +1/+1 counter on Sokka.

Iroh, Grand Lotus

Firebending 2
During your turn, each non-Lesson instant and sorcery card in your graveyard has flashback. The flashback cost is equal to that card's mana cost. (You may cast a card from your graveyard for its flashback cost. Then exile it.)
During your turn, each Lesson card in your graveyard has flashback {1}.

Toph, Earthbending Master

Landfall — Whenever a land you control enters, you get an experience counter.
Whenever you attack, earthbend X, where X is the number of experience counters you have. (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.)

Iroh, Dragon of the West

Haste
Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
At the beginning of combat on your turn, each creature you control with a counter on it gains firebending 2 until end of turn. (Whenever it attacks, add {R}{R}. This mana lasts until end of combat.)

White Lotus Tile

This artifact enters tapped.
{T}: Add X mana of any one color, where X is the greatest number of creatures you control that have a creature type in common.

Sozin's Comet

Each creature you control gains firebending 5 until end of turn. (Whenever it attacks, add {R}{R}{R}{R}{R}. This mana lasts until end of combat.)
Foretell {2}{R} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Crescent Island Temple

When Crescent Island Temple enters, for each Shrine you control, create a 1/1 red Monk creature token with prowess. (Whenever you cast a noncreature spell, it gets +1/+1 until end of turn.)
Whenever another Shrine you control enters, create a 1/1 red Monk creature token with prowess.

Zuko, Firebending Master

First strike
Firebending X, where X is the number of experience counters you have. (Whenever this creature attacks, add X {R}. This mana lasts until end of combat.)
Whenever you cast a spell during combat, you get an experience counter.

Sokka's Haiku

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

Bumi, Eclectic Earthbender

When Bumi 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 Bumi attacks, put two +1/+1 counters on each land creature you control.

Bitter Work

Whenever you attack a player with one or more creatures with power 4 or greater, draw a card.
Exhaust — {4}: Earthbend 4. Activate only during your turn. (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. Activate each exhaust ability only once.)

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.

Kyoshi Island Plaza

When Kyoshi Island Plaza enters, search your library for up to X basic land cards, where X is the number of Shrines you control. Put those cards onto the battlefield tapped, then shuffle.
Whenever another Shrine you control enters, search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Tui and La, Moon and Ocean

Whenever Tui and La become tapped, draw a card.
Whenever Tui and La become untapped, put a +1/+1 counter on them.

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.

Chakra Meditation

When this enchantment enters, return up to one target instant or sorcery card from your graveyard to your hand.
Whenever you cast an instant or sorcery spell, draw a card. Then discard a card unless there are three or more Lesson cards in your graveyard.

Toph, Hardheaded Teacher

When Toph enters, you may discard a card. If you do, return target instant or sorcery card from your graveyard to your hand.
Whenever you cast a spell, earthbend 1. If that spell is a Lesson, put an additional +1/+1 counter on that land. (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.)

Trusty Boomerang

Equipped creature has "{1}, {T}: Tap target creature. Return Trusty Boomerang to its owner's hand."
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

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.

Solid Ground

When this enchantment enters, earthbend 3. (Target land you control becomes a 0/0 creature with haste that's still a land. Put three +1/+1 counters on it. When it dies or is exiled, return it to the battlefield tapped.)
If one or more +1/+1 counters would be put on a permanent you control, that many plus one +1/+1 counters are put on it instead.

Tale of Katara and Toph

Creatures you control have "Whenever this creature becomes tapped for the first time during each of your turns, put a +1/+1 counter on it."

The Spirit Oasis

When The Spirit Oasis enters, draw a card for each Shrine you control.
Whenever another Shrine you control enters, draw a card.