Mountain

Thrill of Possibility

As an additional cost to cast this spell, discard a card.
Draw two cards.

Legion Warboss

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)
At the beginning of combat on your turn, create a 1/1 red Goblin creature token. That token gains haste until end of turn and attacks this combat if able.

Goblin Warchief

Goblin spells you cast cost {1} less to cast.
Goblins you control have haste.

Shared Animosity

Whenever a creature you control attacks, it gets +1/+0 until end of turn for each other attacking creature that shares a creature type with it.

Torch Courier

Haste
Sacrifice Torch Courier: Another target creature gains haste until end of turn.

Rummaging Goblin

Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Koth, Fire of Resistance

+2: Search your library for a basic Mountain card, reveal it, put it into your hand, then shuffle.
−3: Koth, Fire of Resistance deals damage to target creature equal to the number of Mountains you control.
−7: You get an emblem with "Whenever a Mountain you control enters, this emblem deals 4 damage to any target."

Devilish Valet

Trample, haste
Alliance — Whenever another creature you control enters, double Devilish Valet's power until end of turn.

Goblin Motivator

{T}: Target creature gains haste until end of turn. (It can attack and {T} this turn.)

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Umbral Mantle

Equipped creature has "{3}, {Q}: This creature gets +2/+2 until end of turn." ({Q} is the untap symbol.)
Equip {0}

Hobgoblin Bandit Lord

Other Goblins you control get +1/+1.
{R}, {T}: Hobgoblin Bandit Lord deals damage equal to the number of Goblins that entered the battlefield under your control this turn to any target.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Big Score

As an additional cost to cast this spell, discard a card.
Draw two cards and create two Treasure tokens. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Skullclamp

Equipped creature gets +1/-1.
Whenever equipped creature dies, draw two cards.
Equip {1}

Goblin Bombardment

Sacrifice a creature: Goblin Bombardment deals 1 damage to any target.

Mechanized Warfare

If a red or artifact source you control would deal damage to an opponent or a permanent an opponent controls, it deals that much damage plus 1 instead.

Symmetry Matrix

Whenever a creature you control with power equal to its toughness enters, you may pay {1}. If you do, draw a card.

Krenko, Mob Boss

{T}: Create X 1/1 red Goblin creature tokens, where X is the number of Goblins you control.

Chain Reaction

Chain Reaction deals X damage to each creature, where X is the number of creatures on the battlefield.

Empty the Warrens

Create two 1/1 red Goblin creature tokens.
Storm (When you cast this spell, copy it for each spell cast before it this turn.)

Idol of Oblivion

{T}: Draw a card. Activate only if you created a token this turn.
{8}, {T}, Sacrifice Idol of Oblivion: Create a 10/10 colorless Eldrazi creature token.

Path of Ancestry

Path of Ancestry enters tapped.
{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Siege-Gang Commander

When Siege-Gang Commander enters, create three 1/1 red Goblin creature tokens.
{1}{R}, Sacrifice a Goblin: Siege-Gang Commander deals 2 damage to any target.

Forgotten Cave

Forgotten Cave enters tapped.
{T}: Add {R}.
Cycling {R} ({R}, Discard this card: Draw a card.)

Last-Ditch Effort

Sacrifice any number of creatures. Last-Ditch Effort deals that much damage to any target.

Goblin Traprunner

Whenever Goblin Traprunner attacks, flip three coins. For each flip you win, create a 1/1 red Goblin creature token that's tapped and attacking.

Krenko, Tin Street Kingpin

Whenever Krenko, Tin Street Kingpin attacks, put a +1/+1 counter on it, then create a number of 1/1 red Goblin creature tokens equal to Krenko's power.

Mogg War Marshal

Echo {1}{R} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When Mogg War Marshal enters or dies, create a 1/1 red Goblin creature token.

Goblin Instigator

When Goblin Instigator enters, create a 1/1 red Goblin creature token.

City on Fire

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
If a source you control would deal damage to a permanent or player, it deals triple that damage instead.

Dragon Fodder

Create two 1/1 red Goblin creature tokens.

Patriar's Seal

{T}: Add one mana of any color.
{1}, {T}: Untap target legendary creature you control.

Battle Squadron

Flying
Battle Squadron's power and toughness are each equal to the number of creatures you control.

Brightstone Ritual

Add {R} for each Goblin on the battlefield.

Squee, Dubious Monarch

Haste
Whenever Squee, Dubious Monarch attacks, create a 1/1 red Goblin creature token that's tapped and attacking.
You may cast Squee, Dubious Monarch from your graveyard by paying {3}{R} and exiling four other cards from your graveyard rather than paying its mana cost.

Temple of the False God

{T}: Add {C}{C}. Activate only if you control five or more lands.

Goblin Chieftain

Haste (This creature can attack and {T} as soon as it comes under your control.)
Other Goblin creatures you control get +1/+1 and have haste.

Sol Ring

Sword of the Paruns

As long as equipped creature is tapped, tapped creatures you control get +2/+0.
As long as equipped creature is untapped, untapped creatures you control get +0/+2.
{3}: You may tap or untap equipped creature.
Equip {3}

Sting, the Glinting Dagger

Equipped creature gets +1/+1 and has haste.
At the beginning of each combat, untap equipped creature.
Equipped creature has first strike as long as it's blocking or blocked by a Goblin or Orc.
Equip {2}

Goblin Rally

Create four 1/1 red Goblin creature tokens.

Goblin King

Other Goblins get +1/+1 and have mountainwalk.

Impact Tremors

Whenever a creature you control enters, Impact Tremors deals 1 damage to each opponent.

Krenko's Command

Witty Roastmaster

Alliance — Whenever another creature you control enters, Witty Roastmaster deals 1 damage to each opponent.

Moria Marauder

Double strike
Whenever a Goblin or Orc you control deals combat damage to a player, exile the top card of your library. You may play that card this turn.

Castle Embereth

Castle Embereth enters tapped unless you control a Mountain.
{T}: Add {R}.
{1}{R}{R}, {T}: Creatures you control get +1/+0 until end of turn.

Squee, the Immortal

You may cast Squee, the Immortal from your graveyard or from exile.

Beetleback Chief

When Beetleback Chief enters, create two 1/1 red Goblin creature tokens.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Expedite

Target creature gains haste until end of turn.
Draw a card.

Goblin Chirurgeon

Sacrifice a Goblin: Regenerate target creature.

Warstorm Surge

Whenever a creature you control enters, it deals damage equal to its power to any target.

Skirk Prospector

Volley Veteran

When Volley Veteran enters, it deals damage to target creature an opponent controls equal to the number of Goblins you control.

Impulsive Pilferer

When Impulsive Pilferer dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Encore {3}{R} ({3}{R}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Goblin Lookout

{T}, Sacrifice a Goblin: Goblin creatures get +2/+0 until end of turn.

Goblin Picker

Dark-Dweller Oracle

{1}, Sacrifice a creature: Exile the top card of your library. You may play that card this turn. (You still pay its costs. You can play a land this way only if you have an available land play remaining.)

Hazoret's Monument

Red creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, you may discard a card. If you do, draw a card.

Faithless Looting

Draw two cards, then discard two cards.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Goblin Matron

When Goblin Matron enters, you may search your library for a Goblin card, reveal that card, put it into your hand, then shuffle.

Massive Raid

Massive Raid deals damage to any target equal to the number of creatures you control.

Strixhaven Stadium

{T}: Add {C}. Put a point counter on Strixhaven Stadium.
Whenever a creature deals combat damage to you, remove a point counter from Strixhaven Stadium.
Whenever a creature you control deals combat damage to an opponent, put a point counter on Strixhaven Stadium. Then if it has ten or more point counters on it, remove them all and that player loses the game.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

The Autonomous Furnace

The Autonomous Furnace enters tapped.
{T}: Add {R}.
{1}{R}, {T}, Sacrifice The Autonomous Furnace: Draw a card.