Hei Bai, Spirit of Balance

Whenever Hei Bai enters or attacks, you may sacrifice another creature or artifact. If you do, put two +1/+1 counters on Hei Bai.
When Hei Bai leaves the battlefield, put its counters on target creature you control.

Jeong Jeong's Deserters

When this creature enters, put a +1/+1 counter on target creature.

Sokka's Sword Training

Target creature gets +2/+2 until end of turn.
Create a Clue token. (It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Aardvark Sloth

Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Rabaroo Troop

Landfall — Whenever a land you control enters, this creature gains flying until end of turn and you gain 1 life.
Plainscycling {2} ({2}, Discard this card: Search your library for a Plains card, reveal it, put it into your hand, then shuffle.)

Pretending Poxbearers

When this creature dies, create a 1/1 white Ally creature token.

Plains

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.

Path to Redemption

Enchant creature
Enchanted creature can't attack or block.
{5}, Sacrifice this Aura: Exile enchanted creature. Create a 1/1 white Ally creature token. Activate only during your turn.

That's Rough Buddy

Put a +1/+1 counter on target creature. Put two +1/+1 counters on that creature instead if a creature left the battlefield under your control this turn.
Draw a card.

Suki, Courageous Rescuer

Other creatures you control get +1/+0.
Whenever another permanent you control leaves the battlefield during your turn, create a 1/1 white Ally creature token. This ability triggers only once each turn.

Destined Confrontation

Each player chooses any number of creatures they control with total power 4 or less, then sacrifices all other creatures they control.

Thriving Heath

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

Curious Farm Animals

When this creature dies, you gain 3 life.
{2}, Sacrifice this creature: Destroy up to one target artifact or enchantment.