By Force

Ricochet Trap

If an opponent cast a blue spell this turn, you may pay {R} rather than pay this spell's mana cost.
Change the target of target spell with a single target.

Samut's Sprint

Target creature gets +2/+1 and gains haste until end of turn. Scry 1.

Twinflame

Strive — This spell costs {2}{R} more to cast for each target beyond the first.
Choose any number of target creatures you control. For each of them, create a token that's a copy of that creature, except it has haste. Exile those tokens at the beginning of the next end step.

Goblin War Party

Choose one —
• Create three 1/1 red Goblin creature tokens.
• Creatures you control get +1/+1 and gain haste until end of turn.
Entwine {2}{R} (Choose both if you pay the entwine cost.)

Generator Servant

{T}, Sacrifice Generator Servant: Add {C}{C}. If that mana is spent on a creature spell, it gains haste until end of turn. (That creature can attack and {T} as soon as it comes under your control.)

Palladium Myr

Guardian Idol

Guardian Idol enters the battlefield tapped.
{T}: Add {C}.
{2}: Guardian Idol becomes a 2/2 Golem artifact creature until end of turn.

Mogg Salvage

If an opponent controls an Island and you control a Mountain, you may cast this spell without paying its mana cost.
Destroy target artifact.

Prismatic Lens

{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Mogg Alarm

You may sacrifice two Mountains rather than pay this spell's mana cost.
Create two 1/1 red Goblin creature tokens.

Beetleback Chief

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

Firecat Blitz

Create X 1/1 red Elemental Cat creature tokens with haste. Exile them at the beginning of the next end step.
Flashback—{R}{R}, Sacrifice X Mountains. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Chain Reaction

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

Otherworldly Outburst

Target creature gets +1/+0 until end of turn. When that creature dies this turn, create a 3/2 colorless Eldrazi Horror creature token.

Volcanic Offering

Destroy target nonbasic land you don't control and target nonbasic land of an opponent's choice you don't control.
Volcanic Offering deals 7 damage to target creature you don't control and 7 damage to target creature of an opponent's choice you don't control.

Stun

Target creature can't block this turn.
Draw a card.

Iron Myr

Infernal Plunge

As an additional cost to cast this spell, sacrifice a creature.
Add {R}{R}{R}.

Dragon Fodder

Create two 1/1 red Goblin creature tokens.

Siege-Gang Commander

When Siege-Gang Commander enters the battlefield, 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 the battlefield tapped.
{T}: Add {R}.
Cycling {R} ({R}, Discard this card: Draw a card.)

Battle Hymn

Expedite

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

Young Pyromancer

Whenever you cast an instant or sorcery spell, create a 1/1 red Elemental creature token.

Shreds of Sanity

Return up to one target instant card and up to one target sorcery card from your graveyard to your hand, then discard a card. Exile Shreds of Sanity.

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 the battlefield or dies, create a 1/1 red Goblin creature token.

Rile

Rile deals 1 damage to target creature you control. That creature gains trample until end of turn.
Draw a card.

Hordeling Outburst

Create three 1/1 red Goblin creature tokens.

Spark of Creativity

Choose target creature. Exile the top card of your library. You may have Spark of Creativity deal damage to that creature equal to the exiled card's mana value. If you don't, you may play that card until end of turn.

Aftershock

Destroy target artifact, creature, or land. Aftershock deals 3 damage to you.

Kuldotha Rebirth

As an additional cost to cast this spell, sacrifice an artifact.
Create three 1/1 red Goblin creature tokens.

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.

Kari Zev's Expertise

Gain control of target creature or Vehicle until end of turn. Untap it. It gains haste until end of turn.
You may cast a spell with mana value 2 or less from your hand without paying its mana cost.

Millikin

{T}, Mill a card: Add {C}. (To mill a card, put the top card of your library into your graveyard.)

Mishra's Factory

{T}: Add {C}.
{1}: Mishra's Factory becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land.
{T}: Target Assembly-Worker creature gets +1/+1 until end of turn.

Corrupted Grafstone

Corrupted Grafstone enters the battlefield tapped.
{T}: Choose a color of a card in your graveyard. Add one mana of that color.

Outnumber

Outnumber deals damage to target creature equal to the number of creatures you control.

Accelerate

Burn Away

Burn Away deals 6 damage to target creature. When that creature dies this turn, exile its controller's graveyard.

Mizzium Mortars

Mizzium Mortars deals 4 damage to target creature you don't control.
Overload {3}{R}{R}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Goblin Instigator

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

Red Elemental Blast

Choose one —
• Counter target blue spell.
• Destroy target blue permanent.

Manakin

Cathartic Reunion

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

Seething Song

Dwarven Mine

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

Fists of Flame

Draw a card. Until end of turn, target creature gains trample and gets +1/+0 for each card you've drawn this turn.

Walking Atlas

{T}: You may put a land card from your hand onto the battlefield.

Renegade Tactics

Mountain

Krenko's Command

Brightstone Ritual

Add {R} for each Goblin on the battlefield.

Mana Geyser

Add {R} for each tapped land your opponents control.

Skirk Prospector

Honor the God-Pharaoh

As an additional cost to cast this spell, discard a card.
Draw two cards. Amass Zombies 1. (Put a +1/+1 counter on an Army you control. It's also a Zombie. If you don't control an Army, create a 0/0 black Zombie Army creature token first.)

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.)

Reckless Charge

Target creature gets +3/+0 and gains haste until end of turn.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Bolt Bend

This spell costs {3} less to cast if you control a creature with power 4 or greater.
Change the target of target spell or ability with a single target.

Hedron Crawler

{T}: Add {C}. ({C} represents colorless mana.)

Emrakul's Hatcher

When Emrakul's Hatcher enters the battlefield, create three 0/1 colorless Eldrazi Spawn creature tokens. They have "Sacrifice this creature: Add {C}."

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 of your library.)

Runaway Steam-Kin

Whenever you cast a red spell, if Runaway Steam-Kin has fewer than three +1/+1 counters on it, put a +1/+1 counter on Runaway Steam-Kin.
Remove three +1/+1 counters from Runaway Steam-Kin: Add {R}{R}{R}.

Inner Fire

Zada, Hedron Grinder

Whenever you cast an instant or sorcery spell that targets only Zada, Hedron Grinder, copy that spell for each other creature you control that the spell could target. Each copy targets a different one of those creatures.