Mountain

Resistance Skywarden

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

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.

Kiln Fiend

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

Arena Athlete

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

Satyr Hoplite

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

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.)

Uncaged Fury

Target creature gets +1/+1 and gains double strike until end of turn. (It deals both first-strike and regular combat damage.)

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.

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.

Twinferno

Choose one —
• When you cast your next instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.
• Target creature you control gains double strike until end of turn. (It deals both first-strike and regular combat damage.)

Scholar of Combustion

When Scholar of Combustion enters, exile up to one target instant or sorcery card from your graveyard. You may cast that card until the end of your next turn. (You still pay its costs. Timing rules still apply.)

Hearts on Fire

One or two target creatures each get +2/+1 until end of turn.

Frontline Heroism

When Frontline Heroism enters, create a 1/1 red Soldier creature token with haste.
Whenever you cast a spell that targets only a single creature you control, create a 1/1 red Soldier creature token with haste, then copy that spell. The copy targets that token.