Forest

Cracked Earth Technique

Earthbend 3, then earthbend 3. You gain 3 life. (To 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.)

Master's Guidance

Whenever you attack with two or more legendary creatures, put a +1/+1 counter on each of up to two target attacking creatures.
At the beginning of your end step, if you control a creature with power 4 or greater, draw a card.

The Art of Tea

Put a +1/+1 counter on up to one target creature you control. Create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")

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.")

Rocky Rebuke

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

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.

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.")

Thriving Grove

This land enters tapped. As it enters, choose a color other than green.
{T}: Add {G} or one mana of the chosen color.

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.)

Walltop Sentries

Reach, deathtouch
When this creature dies, if there's a Lesson card in your graveyard, you gain 2 life.

Platypus-Bear

Defender
When this creature enters, mill two cards. (Put the top two cards of your library into your graveyard.)
As long as there is a Lesson card in your graveyard, this creature can attack as though it didn't have defender.

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.

Sparring Dummy

Defender
{T}: Mill a card. You may put a land card milled this way into your hand. You gain 2 life if a Lesson card is milled this way. (To mill a card, put the top card of your library into your graveyard.)