Backdraft Hellkite

Flying
Whenever Backdraft Hellkite attacks, each instant and sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost.

Miirym, Sentinel Wyrm

Flying, ward {2}
Whenever another nontoken Dragon you control enters, create a token that's a copy of it, except the token isn't legendary.

Croaking Counterpart

Create a token that's a copy of target non-Frog creature, except it's a 1/1 green Frog.
Flashback {3}{G}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Llanowar Elves

Bogardan Hellkite

Flash
Flying
When Bogardan Hellkite enters, it deals 5 damage divided as you choose among any number of targets.

Dream Pillager

Flying
Whenever Dream Pillager deals combat damage to a player, exile that many cards from the top of your library. Until end of turn, you may cast spells from among those exiled cards.

Undercover Operative

You may have Undercover Operative enter as a copy of any creature on the battlefield, except it enters with a shield counter on it if you control that creature. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

Flameblast Dragon

Flying
Whenever Flameblast Dragon attacks, you may pay {X}{R}. If you do, Flameblast Dragon deals X damage to any target.

Demanding Dragon

Flying
When Demanding Dragon enters, it deals 5 damage to target opponent unless that player sacrifices a creature of their choice.

Vengeful Ancestor

Flying
Whenever Vengeful Ancestor enters or attacks, goad target creature. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)
Whenever a goaded creature attacks, it deals 1 damage to its controller.