Evolving Wilds

{T}, Sacrifice Evolving Wilds: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Legacy Weapon

{W}{U}{B}{R}{G}: Exile target permanent.
If Legacy Weapon would be put into a graveyard from anywhere, reveal Legacy Weapon and shuffle it into its owner's library instead.

Arcane Signet

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

Power Sink

Counter target spell unless its controller pays {X}. If that player doesn't, they tap all lands with mana abilities they control and lose all unspent mana.

Reflecting Pool

{T}: Add one mana of any type that a land you control could produce.

Hydroid Krasis

When you cast this spell, you gain half X life and draw half X cards. Round down each time.
Flying, trample
Hydroid Krasis enters with X +1/+1 counters on it.

Entrancing Melody

Gain control of target creature with mana value X.

Devil's Play

Devil's Play deals X damage to any target.
Flashback {X}{R}{R}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Mikaeus, the Lunarch

Mikaeus, the Lunarch enters with X +1/+1 counters on it.
{T}: Put a +1/+1 counter on Mikaeus.
{T}, Remove a +1/+1 counter from Mikaeus: Put a +1/+1 counter on each other creature you control.

Nikya of the Old Ways

You can't cast noncreature spells.
Whenever you tap a land for mana, add one mana of any type that land produced.

Getting

Gelatinous Genesis

Choking Vines

Cast this spell only during the declare blockers step.
X target attacking creatures become blocked. Choking Vines deals 1 damage to each of those creatures. (This spell works on creatures that can't be blocked.)

Drain Life

Spend only black mana on X.
Drain Life deals X damage to any target. You gain life equal to the damage dealt, but not more life than the player's life total before the damage was dealt, the planeswalker's loyalty before the damage was dealt, or the creature's toughness.

Savage Lands

Savage Lands enters tapped.
{T}: Add {B}, {R}, or {G}.

Vivid Creek

Vivid Creek enters tapped with two charge counters on it.
{T}: Add {U}.
{T}, Remove a charge counter from Vivid Creek: Add one mana of any color.

Plains

Swamp

Mountain

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Boros Signet

Command Tower

Orzhov Signet

Sol Ring

Thriving Isle

Thriving Isle enters tapped. As it enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Boar

Martial Coup

Create X 1/1 white Soldier creature tokens. If X is 5 or more, destroy all other creatures.

Izzet Signet

Vivid Marsh

Vivid Marsh enters tapped with two charge counters on it.
{T}: Add {B}.
{T}, Remove a charge counter from Vivid Marsh: Add one mana of any color.

Omnath, Locus of All

If you would lose unspent mana, that mana becomes black instead.
At the beginning of your first main phase, look at the top card of your library. You may reveal that card if it has three or more colored mana symbols in its mana cost. If you do, add three mana in any combination of its colors and put it into your hand. If you don't reveal it, put it into your hand.

Vivid Grove

Vivid Grove enters tapped with two charge counters on it.
{T}: Add {G}.
{T}, Remove a charge counter from Vivid Grove: Add one mana of any color.

Altered Ego

This spell can't be countered.
You may have Altered Ego enter as a copy of any creature on the battlefield, except it enters with X additional +1/+1 counters on it.

Angel

Vivid Meadow

Vivid Meadow enters tapped with two charge counters on it.
{T}: Add {W}.
{T}, Remove a charge counter from Vivid Meadow: Add one mana of any color.

Mystic Monastery

Mystic Monastery enters tapped.
{T}: Add {U}, {R}, or {W}.

Thriving Heath

Thriving Heath enters tapped. As it enters, choose a color other than white.
{T}: Add {W} or one mana of the chosen color.

Terramorphic Expanse

{T}, Sacrifice Terramorphic Expanse: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Forest

Finale of Glory

Create X 2/2 white Soldier creature tokens with vigilance. If X is 10 or more, also create X 4/4 white Angel creature tokens with flying and vigilance.

Serene Sunset

Prevent all combat damage X target creatures would deal this turn.

Thriving Grove

Thriving Grove enters tapped. As it enters, choose a color other than green.
{T}: Add {G} or one mana of the chosen color.

Burn from Within

Burn from Within deals X damage to any target. If a creature is dealt damage this way, it loses indestructible until end of turn. If that creature would die this turn, exile it instead.

Island

Banefire

Banefire deals X damage to any target.
If X is 5 or more, this spell can't be countered and the damage can't be prevented.

Haunted Screen

{T}: Add {W} or {B}.
{T}, Pay 1 life: Add {G}, {U}, or {R}.
{7}: Put seven +1/+1 counters on Haunted Screen. It becomes a 0/0 Spirit creature in addition to its other types. Activate only once.

Crystal Quarry

{T}: Add {C}.
{5}, {T}: Add {W}{U}{B}{R}{G}.

Kaervek's Torch

As long as Kaervek's Torch is on the stack, spells that target it cost {2} more to cast.
Kaervek's Torch deals X damage to any target.

Divine Deflection

Prevent the next X damage that would be dealt to you and/or permanents you control this turn. If damage is prevented this way, Divine Deflection deals that much damage to any target.

Orochi Hatchery

Orochi Hatchery enters with X charge counters on it.
{5}, {T}: Create a 1/1 green Snake creature token for each charge counter on Orochi Hatchery.

Arcane Sanctum

Arcane Sanctum enters tapped.
{T}: Add {W}, {U}, or {B}.

Nyxborn Hydra

Bestow {X}{G}{G} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.)
Reach, trample
Nyxborn Hydra enters with X +1/+1 counters on it.
Enchanted creature gets +1/+1 for each +1/+1 counter on Nyxborn Hydra and has reach and trample.

Doppelgang

For each of X target permanents, create X tokens that are copies of that permanent.

Regal Behemoth

Trample
When Regal Behemoth enters, you become the monarch.
Whenever you tap a land for mana while you're the monarch, add an additional one mana of any color.

Exponential Growth

Until end of turn, double target creature's power X times.

Soldier

Dimir Signet

Blaze

Vivid Crag

Vivid Crag enters tapped with two charge counters on it.
{T}: Add {R}.
{T}, Remove a charge counter from Vivid Crag: Add one mana of any color.

Snake

Selesnya Signet

Genesis Hydra

When you cast this spell, reveal the top X cards of your library. You may put a nonland permanent card with mana value X or less from among them onto the battlefield. Then shuffle the rest into your library.
Genesis Hydra enters with X +1/+1 counters on it.

Rakdos Signet

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Seaside Citadel

Seaside Citadel enters tapped.
{T}: Add {G}, {W}, or {U}.

Mirari's Wake

Creatures you control get +1/+1.
Whenever you tap a land for mana, add one mana of any type that land produced.

The Monarch

At the beginning of your end step, draw a card.
Whenever a creature deals combat damage to you, its controller becomes the monarch.

Feral Hydra

Feral Hydra enters with X +1/+1 counters on it.
{3}: Put a +1/+1 counter on Feral Hydra. Any player may activate this ability.

Ysgard's Call

Create X 1/1 white Soldier creature tokens. (Then exile this card. You may cast the artifact later from exile.)

Horn of Valhalla

Equipped creature gets +1/+1 for each creature you control.
Equip {3}

Horn of Valhalla // Ysgard's Call

Simic Signet

Jungle Shrine

Jungle Shrine enters tapped.
{T}: Add {R}, {G}, or {W}.

Crumbling Necropolis

Crumbling Necropolis enters tapped.
{T}: Add {U}, {B}, or {R}.

Thriving Moor

Thriving Moor enters tapped. As it enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

Guardian Angel

Prevent the next X damage that would be dealt to any target this turn. Until end of turn, you may pay {1} any time you could cast an instant. If you do, prevent the next 1 damage that would be dealt to that permanent or player this turn.

Frontier Bivouac

Frontier Bivouac enters tapped.
{T}: Add {G}, {U}, or {R}.

Ertai's Meddling

X can't be 0.
Target spell's controller exiles it with X delay counters on it.
At the beginning of each of that player's upkeeps, if that card is exiled, remove a delay counter from it. If the card has no delay counters on it, the player puts it onto the stack as a copy of the original spell.

Black Sun's Zenith

Put X -1/-1 counters on each creature. Shuffle Black Sun's Zenith into its owner's library.

Fabled Passage

{T}, Sacrifice Fabled Passage: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Then if you control four or more lands, untap that land.

Nomad Outpost

Nomad Outpost enters tapped.
{T}: Add {R}, {W}, or {B}.

Ooze

Finale of Revelation

Draw X cards. If X is 10 or more, instead shuffle your graveyard into your library, draw X cards, untap up to five lands, and you have no maximum hand size for the rest of the game.
Exile Finale of Revelation.

Opulent Palace

Opulent Palace enters tapped.
{T}: Add {B}, {G}, or {U}.

Naked Singularity

Cumulative upkeep {3} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
If tapped for mana, Plains produce {R}, Islands produce {G}, Swamps produce {W}, Mountains produce {U}, and Forests produce {B} instead of any other type.

Comet Storm

Multikicker {1} (You may pay an additional {1} any number of times as you cast this spell.)
Choose any target, then choose another target for each time this spell was kicked. Comet Storm deals X damage to each of them.

Hydra

Zaxara, the Exemplary

Deathtouch
{T}: Add two mana of any one color.
Whenever you cast a spell with {X} in its mana cost, create a 0/0 green Hydra creature token, then put X +1/+1 counters on it.

Astral Cornucopia

Astral Cornucopia enters with X charge counters on it.
{T}: Choose a color. Add one mana of that color for each charge counter on Astral Cornucopia.

Extract Brain

Target opponent chooses X cards from their hand. Look at those cards. You may cast a spell from among them without paying its mana cost.

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.

Treasure

{T}, Sacrifice this artifact: Add one mana of any color.

Curse of the Swine

Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.

Unwilling Recruit

Gain control of target creature until end of turn. Untap that creature. It gets +X/+0 and gains haste until end of turn.

Villainous Wealth

Target opponent exiles the top X cards of their library. You may cast any number of spells with mana value X or less from among them without paying their mana costs.

Hell to Pay

Hell to Pay deals X damage to target creature. Create a number of tapped Treasure tokens equal to the amount of excess damage dealt to that creature this way.

Golgari Signet

Mass Manipulation

Gain control of X target creatures and/or planeswalkers.

Wave of Indifference

X target creatures can't block this turn.

Sandsteppe Citadel

Sandsteppe Citadel enters tapped.
{T}: Add {W}, {B}, or {G}.

Ash Barrens

{T}: Add {C}.
Basic landcycling {1} ({1}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Endless One

Endless One enters with X +1/+1 counters on it.

Gruul Signet

Azorius Signet

Debt to the Deathless

Each opponent loses two times X life. You gain life equal to the life lost this way.

Mirage Mesa

Mirage Mesa enters tapped. As it enters, choose a color.
{T}: Add one mana of the chosen color.

Captain's Maneuver

The next X damage that would be dealt to target creature, planeswalker, or player this turn is dealt to another target creature, planeswalker, or player instead.