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.

Rampant Growth

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

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.

Torpor Orb

Creatures entering don't cause abilities to trigger.

Ephemerate

Exile target creature you control, then return it to the battlefield under its owner's control.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Harrow

As an additional cost to cast this spell, sacrifice a land.
Search your library for up to two basic land cards, put them onto the battlefield, then shuffle.

Cloudshift

Exile target creature you control, then return that card to the battlefield under your control.

Mountain

Ley Weaver

Partner with Lore Weaver (When this creature enters, target player may put Lore Weaver into their hand from their library, then shuffle.)
{T}: Untap two target lands.

Saryth, the Viper's Fang

Other tapped creatures you control have deathtouch.
Other untapped creatures you control have hexproof.
{1}, {T}: Untap another target creature or land you control.

Swamp

Forest

Vizier of Tumbling Sands

{T}: Untap another target permanent.
Cycling {1}{U} ({1}{U}, Discard this card: Draw a card.)
When you cycle Vizier of Tumbling Sands, untap target permanent.

Seeker of Skybreak

Razortide Bridge

Razortide Bridge enters tapped.
Indestructible
{T}: Add {W} or {U}.

Momentary Blink

Exile target creature you control, then return it to the battlefield under its owner's control.
Flashback {3}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Crashing Drawbridge

Defender
{T}: Creatures you control gain haste until end of turn.

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.")

Negate

Circuitous Route

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

Niv-Mizzet, the Firemind

Flying
Whenever you draw a card, Niv-Mizzet, the Firemind deals 1 damage to any target.
{T}: Draw a card.

Garth One-Eye

{T}: Choose a card name that hasn't been chosen from among Disenchant, Braingeyser, Terror, Shivan Dragon, Regrowth, and Black Lotus. Create a copy of the card with the chosen name. You may cast the copy. (You still pay its costs.)

Archivist

Dimir Guildgate

Dimir Guildgate enters tapped.
{T}: Add {U} or {B}.

Selesnya Guildgate

Selesnya Guildgate enters tapped.
{T}: Add {G} or {W}.

Exotic Orchard

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

Command Tower

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

Verdant Haven

Enchant land
When Verdant Haven enters, you gain 2 life.
Whenever enchanted land is tapped for mana, its controller adds an additional one mana of any color.

Patriar's Seal

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

Gretchen Titchwillow

{2}{G}{U}: Draw a card. You may put a land card from your hand onto the battlefield.

Painful Truths

Converge — You draw X cards and you lose X life, where X is the number of colors of mana spent to cast this spell.

Kodama's Reach

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.

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.

Stone-Seeder Hierophant

Landfall — Whenever a land you control enters, untap Stone-Seeder Hierophant.
{T}: Untap target land.

Azami, Lady of Scrolls

Tap an untapped Wizard you control: Draw a card.

Door to Nothingness

Door to Nothingness enters tapped.
{W}{W}{U}{U}{B}{B}{R}{R}{G}{G}, {T}, Sacrifice Door to Nothingness: Target player loses the game.

Caustic Tar

Enchant land
Enchanted land has "{T}: Target player loses 3 life."

Cultivate

Search for Tomorrow

Search your library for a basic land card, put it onto the battlefield, then shuffle.
Suspend 2—{G} (Rather than cast this card from your hand, you may pay {G} and exile it with two time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)

Slagwoods Bridge

Slagwoods Bridge enters tapped.
Indestructible
{T}: Add {R} or {G}.

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.

Braingeyser

Terror

Destroy target nonartifact, nonblack creature. It can't be regenerated.

Plains

Gift of Paradise

Enchant land
When Gift of Paradise enters, you gain 3 life.
Enchanted land has "{T}: Add two mana of any one color."

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.

Blossom Dryad

Black Lotus

{T}, Sacrifice Black Lotus: Add three mana of any one color.

Kiora's Follower

Chakram Retriever

Partner with Chakram Slinger (When this creature enters, target player may put Chakram Slinger into their hand from their library, then shuffle.)
Whenever you cast a spell during your turn, untap target creature.

Essence Flux

Exile target creature you control, then return that card to the battlefield under its owner's control. If it's a Spirit, put a +1/+1 counter on it.

Thought Courier

Cliffgate

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

Regrowth

Return target card from your graveyard to your hand.

Tanglepool Bridge

Tanglepool Bridge enters tapped.
Indestructible
{T}: Add {G} or {U}.

Gateway Plaza

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

Navigation Orb

{2}, {T}, Sacrifice Navigation Orb: Search your library for up to two basic land cards and/or Gate cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Temur Ascendancy

Creatures you control have haste.
Whenever a creature you control with power 4 or greater enters, you may draw a card.

Kiora, Behemoth Beckoner

Whenever a creature you control with power 4 or greater enters, draw a card.
−1: Untap target permanent.

Thornglint Bridge

Thornglint Bridge enters tapped.
Indestructible
{T}: Add {G} or {W}.

Island

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.

Voyaging Satyr

Murkfiend Liege

Other green creatures you control get +1/+1.
Other blue creatures you control get +1/+1.
Untap all green and/or blue creatures you control during each other player's untap step.

Shivan Dragon

Flying (This creature can't be blocked except by creatures with flying or reach.)
{R}: Shivan Dragon gets +1/+0 until end of turn.

Farseek

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

Merfolk Looter

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.)

Teleportation Circle

At the beginning of your end step, exile up to one target artifact or creature you control, then return that card to the battlefield under its owner's control.

Enclave Cryptologist

Level up {1}{U} ({1}{U}: Put a level counter on this. Level up only as a sorcery.)
LEVEL 1-2
0/1
{T}: Draw a card, then discard a card.
LEVEL 3+
0/1
{T}: Draw a card.

Soulherder

Whenever a creature is exiled from the battlefield, put a +1/+1 counter on Soulherder.
At the beginning of your end step, you may exile another target creature you control, then return that card to the battlefield under its owner's control.

Kelpie Guide

{T}: Untap another target permanent you control.
{T}: Tap target permanent. Activate only if you control eight or more lands.

Nine-Fingers Keene

Menace
Ward—Pay 9 life.
Whenever Nine-Fingers Keene deals combat damage to a player, look at the top nine cards of your library. You may put a Gate card from among them onto the battlefield. Then if you control nine or more Gates, put the rest into your hand. Otherwise, put the rest on the bottom of your library in a random order.

Plea for Guidance

Search your library for up to two enchantment cards, reveal them, put them into your hand, then shuffle.

Commander's Sphere

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

Darksteel Citadel

Gates Ablaze

Gates Ablaze deals X damage to each creature, where X is the number of Gates you control.

Simic Guildgate

Simic Guildgate enters tapped.
{T}: Add {G} or {U}.

Golgari Guildgate

Golgari Guildgate enters tapped.
{T}: Add {B} or {G}.

Fires of Yavimaya

Creatures you control have haste.
Sacrifice Fires of Yavimaya: Target creature gets +2/+2 until end of turn.

Ghostly Flicker

Exile two target artifacts, creatures, and/or lands you control, then return those cards to the battlefield under your control.

Ley Druid

Dramatic Reversal

Untap all nonland permanents you control.

Gond Gate

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

Izzet Guildgate

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

Ornithopter of Paradise

Market Festival

Enchant land
Whenever enchanted land is tapped for mana, its controller adds an additional two mana in any combination of colors.

Sol Ring

Arcane Signet

Augusta, Dean of Order

Other tapped creatures you control get +1/+0.
Other untapped creatures you control get +0/+1.
Whenever you attack, untap each creature you control, then tap any number of creatures you control.

Plargg, Dean of Chaos

{T}, Discard a card: Draw a card.
{4}{R}, {T}: Reveal cards from the top of your library until you reveal a nonlegendary, nonland card with mana value 3 or less. You may cast that card without paying its mana cost. Put all revealed cards not cast this way on the bottom of your library in a random order.

Plargg, Dean of Chaos // Augusta, Dean of Order

Clever Conjurer

Mage Hand — {T}: Untap target permanent not named Clever Conjurer. Activate only as a sorcery.

Despark

Exile target permanent with mana value 4 or greater.

Azorius Guildgate

Azorius Guildgate enters tapped.
{T}: Add {W} or {U}.

Willing

Creatures you control gain deathtouch and lifelink until end of turn.
Fuse (You may cast one or both halves of this card from your hand.)

Ready

Creatures you control gain indestructible until end of turn. Untap each creature you control.
Fuse (You may cast one or both halves of this card from your hand.)

Ready // Willing

Energy Arc

Untap any number of target creatures. Prevent all combat damage that would be dealt to and dealt by those creatures this turn.

Maze's End

Maze's End enters tapped.
{T}: Add {C}.
{3}, {T}, Return Maze's End 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.

Gruul Guildgate

Gruul Guildgate enters tapped.
{T}: Add {R} or {G}.

Juniper Order Druid

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.

Disenchant

Krosan Restorer

{T}: Untap target land.
Threshold — {T}: Untap up to three target lands. Activate only if seven or more cards are in your graveyard.

Open the Armory

Search your library for an Aura or Equipment card, reveal it, put it into your hand, then shuffle.