Chartooth Cougar

{R}: Chartooth Cougar gets +1/+0 until end of turn.
Mountaincycling {2} ({2}, Discard this card: Search your library for a Mountain card, reveal it, put it into your hand, then shuffle.)

Seismic Strike

Seismic Strike deals damage to target creature equal to the number of Mountains you control.

Searing Blaze

Searing Blaze deals 1 damage to target player or planeswalker and 1 damage to target creature that player or that planeswalker's controller controls.
Landfall — If you had a land enter the battlefield under your control this turn, Searing Blaze deals 3 damage to that player or planeswalker and 3 damage to that creature instead.

Pilgrim's Eye

Flying
When Pilgrim's Eye enters the battlefield, you may search your library for a basic land card, reveal it, put it into your hand, then shuffle.

Geyser Glider

Landfall — Whenever a land enters the battlefield under your control, Geyser Glider gains flying until end of turn.

Aether Membrane

Defender; reach (This creature can block creatures with flying.)
Whenever Aether Membrane blocks a creature, return that creature to its owner's hand at end of combat.

Vulshok Morningstar

Equipped creature gets +2/+2.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Bloodfire Colossus

{R}, Sacrifice Bloodfire Colossus: It deals 6 damage to each creature and each player.

Koth of the Hammer

+1: Untap target Mountain. It becomes a 4/4 red Elemental creature until end of turn. It's still a land.
−2: Add {R} for each Mountain you control.
−5: You get an emblem with "Mountains you control have '{T}: This land deals 1 damage to any target.'"

Vulshok Berserker

Haste (This creature can attack and {T} as soon as it comes under your control.)

Volley of Boulders

Volley of Boulders deals 6 damage divided as you choose among any number of targets.
Flashback {R}{R}{R}{R}{R}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Bloodfire Kavu

{R}, Sacrifice Bloodfire Kavu: It deals 2 damage to each creature.

Vulshok Sorcerer

Haste
{T}: Vulshok Sorcerer deals 1 damage to any target.

Vulshok Battlegear

Equipped creature gets +3/+3.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery. This card enters the battlefield unattached and stays on the battlefield if the creature leaves.)

Stone Giant

{T}: Target creature you control with toughness less than Stone Giant's power gains flying until end of turn. Destroy that creature at the beginning of the next end step.

Anger

Haste
As long as Anger is in your graveyard and you control a Mountain, creatures you control have haste.

Plated Geopede

First strike
Landfall — Whenever a land enters the battlefield under your control, Plated Geopede gets +2/+2 until end of turn.

Wayfarer's Bauble

{2}, {T}, Sacrifice Wayfarer's Bauble: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Torchling

{R}: Untap Torchling.
{R}: Target creature blocks Torchling this turn if able.
{R}: Change the target of target spell that targets only Torchling.
{1}: Torchling gets +1/-1 until end of turn.
{1}: Torchling gets -1/+1 until end of turn.

Lithophage

At the beginning of your upkeep, sacrifice Lithophage unless you sacrifice a Mountain.

Pygmy Pyrosaur

Pygmy Pyrosaur can't block.
{R}: Pygmy Pyrosaur gets +1/+0 until end of turn.

Jaws of Stone

Jaws of Stone deals X damage divided as you choose among any number of targets, where X is the number of Mountains you control as you cast this spell.

Journeyer's Kite

{3}, {T}: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.

Fiery Hellhound

{R}: Fiery Hellhound gets +1/+0 until end of turn.

Cosi's Ravager

Landfall — Whenever a land enters the battlefield under your control, you may have Cosi's Ravager deal 1 damage to target player or planeswalker.

Spire Barrage

Spire Barrage deals damage to any target equal to the number of Mountains you control.

Downhill Charge

You may sacrifice a Mountain rather than pay this spell's mana cost.
Target creature gets +X/+0 until end of turn, where X is the number of Mountains you control.

Greater Stone Spirit

Greater Stone Spirit can't be blocked by creatures with flying.
{2}{R}: Until end of turn, target creature gets +0/+2 and gains "{R}: This creature gets +1/+0 until end of turn."

Mountain

Armillary Sphere

{2}, {T}, Sacrifice Armillary Sphere: Search your library for up to two basic land cards, reveal them, put them into your hand, then shuffle.