Origin of Metalbending

Choose one —
• Destroy target artifact or enchantment.
• Put a +1/+1 counter on target creature you control. It gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

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.")

It'll Quench Ya!

Counter target spell unless its controller pays {2}.

Shared Roots

Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Sokka's Haiku

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

Accumulate Wisdom

Look at the top three cards of your library. Put one of those cards into your hand and the rest on the bottom of your library in any order. Put each of those cards into your hand instead if there are three or more Lesson cards in your graveyard.

Abandon Attachments

You may discard a card. If you do, draw two cards.

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}.

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}.)

Cycle of Renewal

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

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.

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.")