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."

Tectonic Split

As an additional cost to cast this spell, sacrifice half the lands you control, rounded up.
Hexproof
Lands you control have "{T}: Add three mana of any one color."

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.)

Aang, A Lot to Learn

Aang has vigilance as long as there's a Lesson card in your graveyard.
Whenever another creature you control dies, put a +1/+1 counter on Aang.

Hook Swords

Ally

When this Equipment enters, create a 1/1 white Ally creature token, then attach this Equipment to it.
During your turn, equipped creature gets +1/+1 and has first strike.
Equip {3}

Katara, Seeking Revenge

As an additional cost to cast this spell, you may waterbend {2}. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)
When Katara enters, draw a card, then discard a card unless her additional cost was paid.
Katara gets +1/+1 for each Lesson card in your graveyard.

Stand United

Target creature gets +2/+2 until end of turn. If it's an Ally, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Intruder Alarm

Creatures don't untap during their controllers' untap steps.
Whenever a creature enters, untap all creatures.

Zuko, Seeking Honor

Firebending 1 (Whenever this creature attacks, add {R}. This mana lasts until end of combat.)
Whenever you cast a noncreature spell, Zuko gains first strike until end of turn.
Whenever Zuko deals combat damage to a player, put a +1/+1 counter on him.

Acrobatic Leap

Target creature gets +1/+3 and gains flying until end of turn. Untap it.

Cloudshift

Exile target creature you control, then return that card to the battlefield under your control.

Duelist's Heritage

Whenever one or more creatures attack, you may have target attacking creature gain double strike until end of turn.

Valorous Stance

Choose one —
• Target creature gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)
• Destroy target creature with toughness 4 or greater.

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Coastal Piracy

Whenever a creature you control deals combat damage to an opponent, you may draw a card.

Avatar: The Last Airbender Eternal