Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Boulder Rush

Target creature gets +2/+0 until end of turn. (Then exile this card. You may cast the creature later from exile.)

Rimrock Knight

Rimrock Knight // Boulder Rush

Mountain

Valley Dasher

Haste
Valley Dasher attacks each combat if able.

Burning-Tree Emissary

When Burning-Tree Emissary enters, add {R}{G}.

Dwarven Mine

({T}: Add {R}.)
Dwarven Mine enters tapped unless you control three or more other Mountains.
When Dwarven Mine enters untapped, create a 1/1 red Dwarf creature token.

Bogardan Dragonheart

Sacrifice another creature: Until end of turn, Bogardan Dragonheart becomes a Dragon with base power and toughness 4/4, flying, and haste.

Satyr's Cunning

Create a 1/1 red Satyr creature token with "This creature can't block."
Escape—{2}{R}, Exile two other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)

Goblin Cohort

Goblin Cohort can't attack unless you've cast a creature spell this turn.

Fireblast

You may sacrifice two Mountains rather than pay this spell's mana cost.
Fireblast deals 4 damage to any target.

Goblin Grenade

As an additional cost to cast this spell, sacrifice a Goblin.
Goblin Grenade deals 5 damage to any target.

Kiln Fiend

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

Goblin Heelcutter

Whenever Goblin Heelcutter attacks, target creature can't block this turn.
Dash {2}{R} (You may cast this spell for its dash cost. If you do, it gains haste, and it's returned from the battlefield to its owner's hand at the beginning of the next end step.)

Foundry Street Denizen

Whenever another red creature you control enters, Foundry Street Denizen gets +1/+0 until end of turn.

Goblin Bushwhacker

Kicker {R} (You may pay an additional {R} as you cast this spell.)
When Goblin Bushwhacker enters, if it was kicked, creatures you control get +1/+0 and gain haste until end of turn.

Chain Lightning

Chain Lightning deals 3 damage to any target. Then that player or that permanent's controller may pay {R}{R}. If the player does, they may copy this spell and may choose a new target for that copy.