Emberheart Challenger

Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Valiant — Whenever this creature becomes the target of a spell or ability you control for the first time each turn, exile the top card of your library. Until end of turn, you may play that card.

Seedglaive Mentor

Vigilance, haste
Valiant — Whenever this creature becomes the target of a spell or ability you control for the first time each turn, put a +1/+1 counter on it.

Scorching Shot

Scorching Shot deals 5 damage to target creature.

Heartfire Hero

Valiant — Whenever this creature becomes the target of a spell or ability you control for the first time each turn, put a +1/+1 counter on it.
When this creature dies, it deals damage equal to its power to each opponent.

Molten Duplication

Create a token that's a copy of target artifact or creature you control, except it's an artifact in addition to its other types. It gains haste until end of turn. Sacrifice it at the beginning of the next end step.

Lightning Strike

Lightning Strike deals 3 damage to any target.

Monstrous Rage

Target creature gets +2/+0 until end of turn. Create a Monster Role token attached to it. (If you control another Role on it, put that one into the graveyard. Enchanted creature gets +1/+1 and has trample.)

Lightning Helix

Lightning Helix deals 3 damage to any target and you gain 3 life.

Return the Favor

Spree (Choose one or more additional costs.)
+ {1} — Copy target instant spell, sorcery spell, activated ability, or triggered ability. You may choose new targets for the copy.
+ {1} — Change the target of target spell or ability with a single target.