Create a token that's a copy of target creature you control, except it has haste and "At the beginning of the end step, sacrifice this token."
Flashback—, Behold three Elementals. (You may cast this card from your graveyard for its flashback cost. Then exile it. To behold an Elemental, choose an Elemental you control or reveal an Elemental card from your hand.)

Firebending 1 (Whenever this creature attacks, add . This mana lasts until end of combat.)
Lesson spells you cast cost less to cast.

Return up to two target creature cards from your graveyard to your hand. You gain 2 life.

Combustion Technique deals damage equal to 2 plus the number of Lesson cards in your graveyard to target creature. If that creature would die this turn, exile it instead.

Flying
Whenever this creature becomes tapped, another target Merfolk you control gets +2/+0 until end of turn.

Enchant artifact or creature
When this Aura enters, tap enchanted permanent.
Enchanted permanent doesn't untap during its controller's untap step.

When Southern Air Temple enters, put X +1/+1 counters on each creature you control, where X is the number of Shrines you control.
Whenever another Shrine you control enters, put a +1/+1 counter on each creature you control.

When Iroh enters, create a Food token.
At the beginning of combat on your turn, you may have target opponent gain control of target permanent you control. When you do, create a 1/1 white Ally creature token. Put a +1/+1 counter on that token for each permanent you own that your opponents control.

Put a +1/+1 counter on target creature you control. It gains vigilance until end of turn.
Flashback (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Target creature gets +3/+1 until end of turn. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

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.

Destroy target tapped creature.

Destroy target artifact or creature. You gain 1 life.

Return target creature to its owner's hand.
Draw a card.

Whenever you gain life, each opponent loses 1 life.

Enchant permanent
When this Aura enters, you gain 4 life.
Enchanted permanent can't attack or block, and its activated abilities can't be activated unless they're mana abilities.

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

When this creature enters, it deals X damage to target creature an opponent controls, where X is the number of instant and sorcery cards in your graveyard.

When this creature dies, create a 1/1 green Saproling creature token.