Lo and Li, Royal Advisors

Whenever an opponent discards a card or mills one or more cards, put a +1/+1 counter on each Advisor you control.
{2}{U/B}: Target player mills four cards. (They put the top four cards of their library into their graveyard.)

Warship Scout

Jeong Jeong, the Deserter

Firebending 1 (Whenever this creature attacks, add {R}. This mana lasts until end of combat.)
Exhaust — {3}: Put a +1/+1 counter on Jeong Jeong. When you next cast a Lesson spell this turn, copy it and you may choose new targets for the copy.

Messenger Hawk

Flying
When this creature enters, create a Clue token. (It's an artifact with "{2}, Sacrifice this token: Draw a card.")
This creature gets +2/+0 as long as you've drawn two or more cards this turn.

Iguana Parrot

Flying, vigilance
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Twin Blades

Flash
When this Equipment enters, attach it to target creature you control. That creature gains double strike until end of turn.
Equipped creature gets +1/+1.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Zuko, Avatar Hunter

Reach (This creature can block creatures with flying.)
Whenever you cast a red spell, create a 2/2 red Soldier creature token.

Capital Guard

Fire Nation Soldier

Haste (This creature can attack and {T} as soon as it comes under your control.)

Ozai, the Phoenix King

Trample, firebending 4, haste
If you would lose unspent mana, that mana becomes red instead.
Ozai has flying and indestructible as long as you have six or more unspent mana.

Lost in Memories

Flash
Enchant creature you control
Enchanted creature gets +1/+1 and has "Whenever this creature deals combat damage to a player, target instant or sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost." (You may cast that card from your graveyard for its flashback cost. Then exile it.)

Zhao, the Seething Flame

Menace (This creature can't be blocked except by two or more creatures.)

Swampsnare Trap

This spell costs {1} less to cast if it targets a creature with flying.
Enchant creature
Enchanted creature gets -5/-3.

Fire Nation Archers

Reach (This creature can block creatures with flying.)
{5}: This creature deals 2 damage to each opponent. Create a 2/2 red Soldier creature token.

Meteor Sword

When this Equipment enters, destroy target permanent.
Equipped creature gets +3/+3.
Equip {3} ({3}:Attach to target creature you control. Equip only as a sorcery.)