Force of Negation

If it's not your turn, you may exile a blue card from your hand rather than pay this spell's mana cost.
Counter target noncreature spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Allosaurus Rider

You may exile two green cards from your hand rather than pay this spell's mana cost.
Allosaurus Rider's power and toughness are each equal to 1 plus the number of lands you control.

Skyshroud Cutter

If you control a Forest, rather than pay this spell's mana cost, you may have each other player gain 5 life.

Pulverize

You may sacrifice two Mountains rather than pay this spell's mana cost.
Destroy all artifacts.

Daze

You may return an Island you control to its owner's hand rather than pay this spell's mana cost.
Counter target spell unless its controller pays {1}.

Dark Triumph

If you control a Swamp, you may sacrifice a creature rather than pay this spell's mana cost.
Creatures you control get +2/+0 until end of turn.

Force of Virtue

If it's not your turn, you may exile a white card from your hand rather than pay this spell's mana cost.
Flash
Creatures you control get +1/+1.

Nourishing Shoal

You may exile a green card with mana value X from your hand rather than pay this spell's mana cost.
You gain X life.

Thunderclap

You may sacrifice a Mountain rather than pay this spell's mana cost.
Thunderclap deals 3 damage to target creature.

Outbreak

You may discard a Swamp card rather than pay this spell's mana cost.
Choose a creature type. All creatures of that type get -1/-1 until end of turn.

Delraich

You may sacrifice three black creatures rather than pay this spell's mana cost.
Trample

Fireblast

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

Ramosian Rally

If you control a Plains, you may tap an untapped creature you control rather than pay this spell's mana cost.
Creatures you control get +1/+1 until end of turn.

Fury of the Horde

You may exile two red cards from your hand rather than pay this spell's mana cost.
Untap all creatures that attacked this turn. After this main phase, there is an additional combat phase followed by an additional main phase.

Demon of Death's Gate

You may pay 6 life and sacrifice three black creatures rather than pay this spell's mana cost.
Flying, trample

Sivvi's Valor

If you control a Plains, you may tap an untapped creature you control rather than pay this spell's mana cost.
All damage that would be dealt to target creature this turn is dealt to you instead.

Mine Collapse

If it's your turn, you may sacrifice a Mountain rather than pay this spell's mana cost.
Mine Collapse deals 5 damage to target creature or planeswalker.

Reverent Silence

If you control a Forest, rather than pay this spell's mana cost, you may have each other player gain 6 life.
Destroy all enchantments.

Mindbreak Trap

If an opponent cast three or more spells this turn, you may pay {0} rather than pay this spell's mana cost.
Exile any number of target spells.

Pyrokinesis

You may exile a red card from your hand rather than pay this spell's mana cost.
Pyrokinesis deals 4 damage divided as you choose among any number of target creatures.

Shining Shoal

You may exile a white card with mana value X from your hand rather than pay this spell's mana cost.
The next X damage that a source of your choice would deal to you and/or creatures you control this turn is dealt to any target instead.

Gush

You may return two Islands you control to their owner's hand rather than pay this spell's mana cost.
Draw two cards.

Snuff Out

If you control a Swamp, you may pay 4 life rather than pay this spell's mana cost.
Destroy target nonblack creature. It can't be regenerated.

Angelic Favor

If you control a Plains, you may tap an untapped creature you control rather than pay this spell's mana cost.
Cast this spell only during combat.
Create a 4/4 white Angel creature token with flying. Exile it at the beginning of the next end step.

Force of Rage

If it's not your turn, you may exile a red card from your hand rather than pay this spell's mana cost.
Create two 3/1 red Elemental creature tokens with trample and haste. Sacrifice those tokens at the beginning of your next upkeep.

Soul Spike

You may exile two black cards from your hand rather than pay this spell's mana cost.
Soul Spike deals 4 damage to any target and you gain 4 life.

Abolish

You may discard a Plains card rather than pay this spell's mana cost.
Destroy target artifact or enchantment.

Orim's Cure

If you control a Plains, you may tap an untapped creature you control rather than pay this spell's mana cost.
Prevent the next 4 damage that would be dealt to any target this turn.

Force of Despair

If it's not your turn, you may exile a black card from your hand rather than pay this spell's mana cost.
Destroy all creatures that entered this turn.

Misdirection

You may exile a blue card from your hand rather than pay this spell's mana cost.
Change the target of target spell with a single target.

Flameshot

You may discard a Mountain card rather than pay this spell's mana cost.
Flameshot deals 3 damage divided as you choose among one, two, or three target creatures.

Ensnare

You may return two Islands you control to their owner's hand rather than pay this spell's mana cost.
Tap all creatures.

Contagion

You may pay 1 life and exile a black card from your hand rather than pay this spell's mana cost.
Distribute two -2/-1 counters among one or two target creatures.

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.

Sunscour

You may exile two white cards from your hand rather than pay this spell's mana cost.
Destroy all creatures.

Reverent Mantra

You may exile a white card from your hand rather than pay this spell's mana cost.
Choose a color. All creatures gain protection from the chosen color until end of turn.

Mogg Alarm

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

Tidal Bore

You may return an Island you control to its owner's hand rather than pay this spell's mana cost.
You may tap or untap target creature.

Land Grant

If you have no land cards in hand, you may reveal your hand rather than pay this spell's mana cost.
Search your library for a Forest card, reveal that card, put it into your hand, then shuffle.

Summoning Trap

If a creature spell you cast this turn was countered by a spell or ability an opponent controlled, you may pay {0} rather than pay this spell's mana cost.
Look at the top seven cards of your library. You may put a creature card from among them onto the battlefield. Put the rest on the bottom of your library in any order.

Cave-In

You may exile a red card from your hand rather than pay this spell's mana cost.
Cave-In deals 2 damage to each creature and each player.

Spinning Darkness

You may exile the top three black cards of your graveyard rather than pay this spell's mana cost.
Spinning Darkness deals 3 damage to target nonblack creature. You gain 3 life.

Force of Vigor

If it's not your turn, you may exile a green card from your hand rather than pay this spell's mana cost.
Destroy up to two target artifacts and/or enchantments.

Lashknife

If you control a Plains, you may tap an untapped creature you control rather than pay this spell's mana cost.
Enchant creature
Enchanted creature has first strike.

New Perspectives

When New Perspectives enters, draw three cards.
As long as you have seven or more cards in hand, you may pay {0} rather than pay cycling costs.

Commandeer

You may exile two blue cards from your hand rather than pay this spell's mana cost.
Gain control of target noncreature spell. You may choose new targets for it. (If that spell is an artifact, enchantment, or planeswalker, the permanent enters under your control.)

Thwart

You may return three Islands you control to their owner's hand rather than pay this spell's mana cost.
Counter target spell.

Unmask

You may exile a black card from your hand rather than pay this spell's mana cost.
Target player reveals their hand. You choose a nonland card from it. That player discards that card.

Crash

You may sacrifice a Mountain rather than pay this spell's mana cost.
Destroy target artifact.

Invigorate

If you control a Forest, rather than pay this spell's mana cost, you may have an opponent gain 3 life.
Target creature gets +4/+4 until end of turn.

Sickening Shoal

You may exile a black card with mana value X from your hand rather than pay this spell's mana cost.
Target creature gets -X/-X until end of turn.

Vine Dryad

You may exile a green card from your hand rather than pay this spell's mana cost.
Flash
Forestwalk (This creature can't be blocked as long as defending player controls a Forest.)

Mind Swords

If you control a Swamp, you may sacrifice a creature rather than pay this spell's mana cost.
Each player exiles two cards from their hand.

Salvage Titan

You may sacrifice three artifacts rather than pay this spell's mana cost.
Exile three artifact cards from your graveyard: Return Salvage Titan from your graveyard to your hand.

Archive Trap

If an opponent searched their library this turn, you may pay {0} rather than pay this spell's mana cost.
Target opponent mills thirteen cards.

Snapback

You may exile a blue card from your hand rather than pay this spell's mana cost.
Return target creature to its owner's hand.

Force of Will

You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost.
Counter target spell.

Foil

You may discard an Island card and another card rather than pay this spell's mana cost.
Counter target spell.

Snag

You may discard a Forest card rather than pay this spell's mana cost.
Prevent all combat damage that would be dealt by unblocked creatures this turn.

Disrupting Shoal

You may exile a blue card with mana value X from your hand rather than pay this spell's mana cost.
Counter target spell if its mana value is X.

Blazing Shoal

You may exile a red card with mana value X from your hand rather than pay this spell's mana cost.
Target creature gets +X/+0 until end of turn.

Dream Halls

Rather than pay the mana cost for a spell, its controller may discard a card that shares a color with that spell.

Bounty of the Hunt

You may exile a green card from your hand rather than pay this spell's mana cost.
Distribute three +1/+1 counters among one, two, or three target creatures. For each +1/+1 counter you put on a creature this way, remove a +1/+1 counter from that creature at the beginning of the next cleanup step.

Ravenous Trap

If an opponent had three or more cards put into their graveyard from anywhere this turn, you may pay {0} rather than pay this spell's mana cost.
Exile target player's graveyard.