Explore the Underdark

Search your library for up to two basic land cards and/or Gate cards, put them onto the battlefield tapped, then shuffle.
You take the initiative.

Sol Ring

Dimir Guildgate

This land enters tapped.
{T}: Add {U} or {B}.

Swamp

See Double

This spell can't be copied.
Choose one. If an opponent has eight or more cards in their graveyard, you may choose both instead.
• Copy target spell. You may choose new targets for the copy. (A copy of a permanent spell becomes a token.)
• Create a token that's a copy of target creature.

Ral, Storm Conduit

Whenever you cast or copy an instant or sorcery spell, Ral, Storm Conduit deals 1 damage to target opponent or planeswalker.
+2: Scry 1.
−2: When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.

Fracture

Destroy target artifact, enchantment, or planeswalker.

Boros Guildgate

This land enters tapped.
{T}: Add {R} or {W}.

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.

Baldur's Gate

{T}: Add {C}.
{2}, {T}: Add X mana of any one color, where X is the number of other Gates you control.

Bedevil

Destroy target artifact, creature, or planeswalker.

Increasing Vengeance

Copy target instant or sorcery spell you control. If this spell was cast from a graveyard, copy that spell twice instead. You may choose new targets for the copies.
Flashback {3}{R}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Heap Gate

{T}: Add {C}.
{1}, {T}: Add one mana of any color.
{1}, {T}, Tap an untapped Gate you control: Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Practical Research

Draw four cards. Then discard two cards unless you discard an instant or sorcery card.

Faithful Mending

You gain 2 life, draw two cards, then discard two cards.
Flashback {1}{W}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Putrefy

Destroy target artifact or creature. It can't be regenerated.

Reinterpret

Counter target spell. You may cast a spell with equal or lesser mana value from your hand without paying its mana cost.

Island

Narset's Reversal

Copy target instant or sorcery spell, then return it to its owner's hand. You may choose new targets for the copy.

Gruul Guildgate

This land enters tapped.
{T}: Add {R} or {G}.

Arcane Signet

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

Exotic Orchard

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

Witherbloom Apprentice

Magecraft — Whenever you cast or copy an instant or sorcery spell, each opponent loses 1 life and you gain 1 life.

Merciless Eviction

Choose one —
• Exile all artifacts.
• Exile all creatures.
• Exile all enchantments.
• Exile all planeswalkers.

Sea Gate

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

Azorius Guildgate

This land enters tapped.
{T}: Add {W} or {U}.

Supreme Verdict

This spell can't be countered.
Destroy all creatures.

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Despark

Exile target permanent with mana value 4 or greater.

Secrets of the Dead

Whenever you cast a spell from your graveyard, draw a card.

Nature's Lore

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Manamorphose

Add two mana in any combination of colors.
Draw a card.

Ringsight

The Ring tempts you. Search your library for a card that shares a color with a legendary creature you control, reveal it, put it into your hand, then shuffle.

Citadel Gate

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

Chandra, Hope's Beacon

Whenever you cast an instant or sorcery spell, copy it. You may choose new targets for the copy. This ability triggers only once each turn.
+2: Add two mana in any combination of colors.
+1: Exile the top five cards of your library. Until the end of your next turn, you may cast an instant or sorcery spell from among those exiled cards.
−X: Chandra, Hope's Beacon deals X damage to each of up to two targets.

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.

Niv-Mizzet Reborn

Flying
When Niv-Mizzet Reborn enters, reveal the top ten cards of your library. For each color pair, choose a card that's exactly those colors from among them. Put the chosen cards into your hand and the rest on the bottom of your library in a random order.

Rakdos Charm

Choose one —
• Exile target player's graveyard.
• Destroy target artifact.
• Each creature deals 1 damage to its controller.

Mortify

Reiterate

Buyback {3} (You may pay an additional {3} as you cast this spell. If you do, put this card into your hand as it resolves.)
Copy target instant or sorcery spell. You may choose new targets for the copy.

Eureka Moment

Draw two cards. You may put a land card from your hand onto the battlefield.

Gond Gate

Gates you control enter untapped.
{T}: Add {C}.
{T}: Add one mana of any color that a Gate you control could produce.

Ionize

Counter target spell. Ionize deals 2 damage to that spell's controller.

Black Dragon Gate

Black Dragon Gate enters tapped.
As Black Dragon Gate enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

Gateway Plaza

Gateway Plaza enters tapped.
When Gateway Plaza enters, sacrifice it unless you pay {1}.
{T}: Add one mana of any color.

Galvanic Iteration

When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.
Flashback {1}{U}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Cosmic Rebirth

Choose target permanent card in your graveyard. If it has mana value 3 or less, you may put it onto the battlefield. If you don't put it onto the battlefield, put it into your hand.
You gain 3 life.

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

Vega, the Watcher

Flying
Whenever you cast a spell from anywhere other than your hand, draw a card.

Countersquall

Counter target noncreature spell. Its controller loses 2 life.

Rakdos Guildgate

This land enters tapped.
{T}: Add {B} or {R}.

Orzhov Guildgate

This land enters tapped.
{T}: Add {W} or {B}.

Simic Guildgate

This land enters tapped.
{T}: Add {G} or {U}.

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Quandrix Apprentice

Magecraft — Whenever you cast or copy an instant or sorcery spell, look at the top three cards of your library. You may reveal a land card from among them and put that card into your hand. Put the rest on the bottom of your library in any order.

Selesnya Guildgate

This land enters tapped.
{T}: Add {G} or {W}.

Mountain

Storm King's Thunder

When you next cast an instant or sorcery spell this turn, copy that spell X times. You may choose new targets for the copies.

Maze's End

This land enters tapped.
{T}: Add {C}.
{3}, {T}, Return this land to its owner's hand: Search your library for a Gate card, put it onto the battlefield, then shuffle. If you control ten or more Gates with different names, you win the game.

Mana Cannons

Whenever you cast a multicolored spell, Mana Cannons deals X damage to any target, where X is the number of colors that spell is.

Abrupt Decay

This spell can't be countered.
Destroy target nonland permanent with mana value 3 or less.

Storm-Kiln Artist

Storm-Kiln Artist gets +1/+0 for each artifact you control.
Magecraft — Whenever you cast or copy an instant or sorcery spell, create a Treasure token.

Urban Evolution

Draw three cards. You may play an additional land this turn.

Prismari Command

Choose two —
• Prismari Command deals 2 damage to any target.
• Target player draws two cards, then discards two cards.
• Target player creates a Treasure token.
• Destroy target artifact.

General Ferrous Rokiric

Hexproof from monocolored
Whenever you cast a multicolored spell, create a 4/4 red and white Golem artifact creature token.

Explosion

Explosion deals X damage to any target. Target player draws X cards.

Expansion

Copy target instant or sorcery spell with mana value 4 or less. You may choose new targets for the copy.

Expansion // Explosion

Tome of the Guildpact

Whenever you cast a multicolored spell, draw a card.
{T}: Add one mana of any color.

Cascading Cataracts

Indestructible
{T}: Add {C}.
{5}, {T}: Add five mana in any combination of colors.

Forest

Plains

Izzet Charm

Choose one —
• Counter target noncreature spell unless its controller pays {2}.
• Izzet Charm deals 2 damage to target creature.
• Draw two cards, then discard two cards.

Basilisk Gate

{T}: Add {C}.
{2}, {T}: Target creature gets +X/+X until end of turn, where X is the number of Gates you control. Activate only as a sorcery.

Counterflux

This spell can't be countered.
Counter target spell you don't control.
Overload {1}{U}{U}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Professor Onyx

Magecraft — Whenever you cast or copy an instant or sorcery spell, each opponent loses 2 life and you gain 2 life.
+1: You lose 1 life. Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.
−3: Each opponent sacrifices a creature with the greatest power among creatures that player controls.
−8: Each opponent may discard a card. If they don't, they lose 3 life. Repeat this process six more times.

Wilderness Reclamation

At the beginning of your end step, untap all lands you control.

Izzet Guildgate

Izzet Guildgate enters tapped.
{T}: Add {U} or {R}.

Boros Charm

Choose one —
• Boros Charm deals 4 damage to target player or planeswalker.
• Permanents you control gain indestructible until end of turn.
• Target creature gains double strike until end of turn.

Archmage Emeritus

Magecraft — Whenever you cast or copy an instant or sorcery spell, draw a card.

Goblin Electromancer

Instant and sorcery spells you cast cost {1} less to cast.

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Golgari Guildgate

This land enters tapped.
{T}: Add {B} or {G}.

Vindicate

Kodama's Reach

Swarm Intelligence

Whenever you cast an instant or sorcery spell, you may copy that spell. You may choose new targets for the copy.

Command Tower

Circuitous Route

Search your library for up to two basic land cards and/or Gate cards, put them onto the battlefield tapped, then shuffle.

Terminate

Destroy target creature. It can't be regenerated.

Manor Gate

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

Thousand-Year Storm

Whenever you cast an instant or sorcery spell, copy it for each other instant and sorcery spell you've cast before it this turn. You may choose new targets for the copies.

Cliffgate

Cliffgate enters tapped.
As Cliffgate enters, choose a color other than red.
{T}: Add {R} or one mana of the chosen color.

Niv-Mizzet, Supreme

Flying, hexproof from monocolored
Each instant and sorcery card in your graveyard that's exactly two colors has jump-start. (You may cast that card from your graveyard by discarding a card in addition to paying its other costs. Then exile it.)