Kiln Fiend

Whenever you cast an instant or sorcery spell, Kiln Fiend gets +3/+0 until end of turn.

Cleon, Merry Champion

Double strike
Heroic — Whenever you cast a spell that targets Cleon, exile the top card of your library. You may play that card until the end of your next turn.

Arena Athlete

Heroic — Whenever you cast a spell that targets Arena Athlete, target creature an opponent controls can't block this turn.

Hero of the Games

Whenever you cast a spell that targets Hero of the Games, creatures you control get +1/+0 until end of turn.

Titan's Strength

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.)

Dreadhorde Arcanist

Trample
Whenever Dreadhorde Arcanist attacks, you may cast target instant or sorcery card with mana value less than or equal to Dreadhorde Arcanist's power from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.

Roil Eruption

Kicker {5} (You may pay an additional {5} as you cast this spell.)
Roil Eruption deals 3 damage to any target. If this spell was kicked, it deals 5 damage instead.

Coordinated Assault

Up to two target creatures each get +1/+0 and gain first strike until end of turn. (They deal combat damage before creatures without first strike.)

Unleash Fury

Double the power of target creature until end of turn.

Mountain

Satyr Hoplite

Heroic — Whenever you cast a spell that targets Satyr Hoplite, put a +1/+1 counter on Satyr Hoplite.

Thriving Bluff

Thriving Bluff enters tapped. As it enters, choose a color other than red.
{T}: Add {R} or one mana of the chosen color.

Resistance Skywarden

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