Mountain

Atarka Pummeler

Formidable — {3}{R}{R}: Creatures you control gain menace until end of turn. Activate only if creatures you control have total power 8 or greater. (They can't be blocked except by two or more creatures.)

Fall of the Hammer

Target creature you control deals damage equal to its power to another target creature.

Anax, Hardened in the Forge

Anax's power is equal to your devotion to red. (Each {R} in the mana costs of permanents you control counts toward your devotion to red.)
Whenever Anax or another nontoken creature you control dies, create a 1/1 red Satyr creature token with "This creature can't block." If the creature had power 4 or greater, create two of those tokens instead.

Dragon Whisperer

{R}: Dragon Whisperer gains flying until end of turn.
{1}{R}: Dragon Whisperer gets +1/+0 until end of turn.
Formidable — {4}{R}{R}: Create a 4/4 red Dragon creature token with flying. Activate only if creatures you control have total power 8 or greater.

Stampede Rider

Trample
At the beginning of each combat, if you control a creature with power 4 or greater, Stampede Rider gets +1/+1 until end of turn.

Furious Rise

At the beginning of your end step, if you control a creature with power 4 or greater, exile the top card of your library. You may play that card until you exile another card with Furious Rise.

Flametongue Kavu

When Flametongue Kavu enters, it deals 4 damage to target creature.

Flames of the Raze-Boar

Flames of the Raze-Boar deals 4 damage to target creature an opponent controls. Then Flames of the Raze-Boar deals 2 damage to each other creature that player controls if you control a creature with power 4 or greater.

Volcanic Salvo

This spell costs {X} less to cast, where X is the total power of creatures you control.
Volcanic Salvo deals 6 damage to each of up to two target creatures and/or planeswalkers.

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.

Temur Battle Rage

Target creature gains double strike until end of turn.
Ferocious — That creature also gains trample until end of turn if you control a creature with power 4 or greater.

Flamewake Phoenix

Flying, haste
This creature attacks each combat if able.
At the beginning of combat on your turn, if you control a creature with power 4 or greater, you may pay {R}. If you do, return this card from your graveyard to the battlefield.

Vexing Devil

When Vexing Devil enters, any opponent may have it deal 4 damage to them. If a player does, sacrifice Vexing Devil.