Snakeskin Veil

Put a +1/+1 counter on target creature you control. It gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

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.

Firebending Lesson

Kicker {4} (You may pay an additional {4} as you cast this spell.)
Firebending Lesson deals 2 damage to target creature. If this spell was kicked, it deals 5 damage to that creature instead.

Llanowar Elves

Rumble Arena

Vigilance
When this land enters, scry 1. (Look at the top card of your library. You may put it on the bottom.)
{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Mountain

Stomping Ground

({T}: Add {R} or {G}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Ba Sing Se

This land enters tapped unless you control a basic land.
{T}: Add {G}.
{2}{G}, {T}: Earthbend 2. Activate only as a sorcery. (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.)

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.)

Fuel the Flames

Fuel the Flames deals 2 damage to each creature.
Cycling {2} ({2}, Discard this card: Draw a card.)

Scarlet Spider, Ben Reilly

Web-slinging {R}{G} (You may cast this spell for {R}{G} if you also return a tapped creature you control to its owner's hand.)
Trample
Sensational Save — If Scarlet Spider was cast using web-slinging, he enters with X +1/+1 counters on him, where X is the mana value of the returned creature.

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.)

Spider Manifestation

Reach
{T}: Add {R} or {G}.
Whenever you cast a spell with mana value 4 or greater, untap this creature.

Michelangelo, Mutant BFF

Each creature you control with a counter on it can't be blocked by more than one creature.
Whenever Michelangelo enters or attacks, create a Mutagen token. (It's an artifact with "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")

Scrapshooter

Gift a card (You may promise an opponent a gift as you cast this spell. If you do, when it enters, they draw a card.)
Reach
When this creature enters, if the gift was promised, destroy target artifact or enchantment an opponent controls.

Forest

Gnarlid Colony

Kicker {2}{G} (You may pay an additional {2}{G} as you cast this spell.)
If this creature was kicked, it enters with two +1/+1 counters on it.
Each creature you control with a +1/+1 counter on it has trample. (It can deal excess combat damage to the player or planeswalker it's attacking.)

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.)