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.

It That Betrays

Annihilator 2 (Whenever this creature attacks, defending player sacrifices two permanents of their choice.)
Whenever an opponent sacrifices a nontoken permanent, put that card onto the battlefield under your control.

Crop Rotation

As an additional cost to cast this spell, sacrifice a land.
Search your library for a land card, put that card onto the battlefield, then shuffle.

Dungeoneer's Pack

This artifact enters tapped.
{2}, {T}, Sacrifice this artifact: You take the initiative, gain 3 life, draw a card, and create a Treasure token. Activate only as a sorcery. (A Treasure token is an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Snow-Covered Swamp

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

White Plume Adventurer

When this creature enters, you take the initiative.
At the beginning of each opponent's upkeep, untap a creature you control. If you've completed a dungeon, untap all creatures you control instead.

Gateway Plaza

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

Gruul Signet

Golgari Guildgate

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

Underdark Explorer

Menace (This creature can't be blocked except by two or more creatures.)
When this creature enters, you take the initiative.

Rilsa Rael, Kingpin

Deathtouch
When Rilsa Rael enters, you take the initiative.
Whenever you attack, target attacking creature gains deathtouch until end of turn. If you've completed a dungeon, that creature also gets +5/+0 and gains first strike and menace until end of turn.

Orzhov Signet

Snow-Covered Forest

Unmake

Dimir Guildgate

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

Genesis Ultimatum

Look at the top five cards of your library. Put any number of permanent cards from among them onto the battlefield and the rest into your hand. Exile Genesis Ultimatum.

Ravenloft Adventurer

When this creature enters, you take the initiative.
If a creature an opponent controls would die, instead exile it and put a hit counter on it.
Whenever this creature attacks, if you've completed a dungeon, defending player loses 1 life for each card they own in exile with a hit counter on it.

Golgari Signet

Panharmonicon

If an artifact or creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Loxodon Gatekeeper

Artifacts, creatures, and lands your opponents control enter tapped.

Eerie Ultimatum

Return any number of permanent cards with different names from your graveyard to the battlefield.

Boros Signet

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

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.

Selesnya Guildgate

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

Sea Gate

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

Tazri, Beacon of Unity

This spell costs {1} less to cast for each creature in your party.
{2/U}{2/B}{2/R}{2/G}: Look at the top six cards of your library. You may reveal up to two Cleric, Rogue, Warrior, Wizard, and/or Ally cards from among them and put them into your hand. Put the rest on the bottom of your library in a random order.

Forest

Dimir Signet

Snow-Covered Island

Eternal Witness

When this creature enters, you may return target card from your graveyard to your hand.

Brilliant Ultimatum

Exile the top five cards of your library. An opponent separates those cards into two piles. You may play lands and cast spells from one of those piles. If you cast a spell this way, you cast it without paying its mana cost.

Reality Shift

Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)

Ruinous Ultimatum

Destroy all nonland permanents your opponents control.

Feywild Caretaker

When this creature enters, you take the initiative.
At the beginning of your end step, if you have the initiative, create a 1/1 blue Faerie Dragon creature token with flying.

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.

Simic Signet

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.

Emergent Ultimatum

Search your library for up to three monocolored cards with different names and exile them. An opponent chooses one of those cards. Shuffle that card into your library. You may cast the other cards without paying their mana costs. Exile Emergent Ultimatum.

Island

Boros Guildgate

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

Mountain

Gond Gate

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

Tiller Engine

Whenever a land you control enters tapped, choose one —
• Untap that land.
• Tap target nonland permanent an opponent controls.

Swamp

Trailblazer's Torch

When this Equipment enters, you take the initiative.
Whenever equipped creature becomes blocked, it deals 2 damage to each creature blocking it.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Gatecreeper Vine

Defender
When this creature enters, you may search your library for a basic land card or a Gate card, reveal it, put it into your hand, then shuffle.

Seasoned Dungeoneer

When this creature enters, you take the initiative.
Whenever you attack, target attacking Cleric, Rogue, Warrior, or Wizard gains protection from creatures until end of turn. It explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on the creature, then put the card back or put it into your graveyard.)

Orzhov Guildgate

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

Anguished Unmaking

Exile target nonland permanent. You lose 3 life.

Selesnya Signet

Snow-Covered Mountain

Urabrask the Hidden

Creatures you control have haste.
Creatures your opponents control enter tapped.

Snow-Covered Plains

From the Catacombs

Put target creature card from a graveyard onto the battlefield under your control with a corpse counter on it. You take the initiative. If that creature would leave the battlefield, exile it instead of putting it anywhere else.
Escape—{3}{B}{B}, Exile five other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)

Citadel Gate

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

Manor Gate

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

Gruul Guildgate

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

Sarevok's Tome

When this artifact enters, you take the initiative.
{T}: Add {C}. If you have the initiative, add {C}{C} instead.
{3}, {T}: Exile cards from the top of your library until you exile a nonland card. You may cast that card without paying its mana cost. Activate only if you've completed a dungeon.

Vicious Battlerager

When this creature enters, you take the initiative.
Spiked Retribution — Whenever this creature becomes blocked by a creature, that creature's controller loses 5 life.

Azorius Guildgate

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

Inspired Ultimatum

Target player gains 5 life, Inspired Ultimatum deals 5 damage to any target, then you draw five cards.

Caves of Chaos Adventurer

Trample
When this creature enters, you take the initiative.
Whenever this creature attacks, exile the top card of your library. If you've completed a dungeon, you may play that card this turn without paying its mana cost. Otherwise, you may play that card this turn.

Void Winnower

Your opponents can't cast spells with even mana values. (Zero is even.)
Your opponents can't block with creatures with even mana values.

Loot Dispute

When this enchantment enters, you take the initiative and create a Treasure token.
Whenever you attack the player who has the initiative, create a Treasure token.
Loud Ruckus — Whenever you complete a dungeon, create a 5/5 red Dragon creature token with flying.

Stirring Bard

Defender
When this creature enters, you take the initiative.
Mantle of Inspiration — {T}: Target creature gains menace and haste until end of turn.

Aarakocra Sneak

Flying
When this creature enters, you take the initiative.

Passageway Seer

Lifelink
When this creature enters, you take the initiative.
At the beginning of your end step, if you have the initiative, put a +1/+1 counter on this creature.

Ulamog, the Infinite Gyre

When you cast this spell, destroy target permanent.
Indestructible
Annihilator 4 (Whenever this creature attacks, defending player sacrifices four permanents of their choice.)
When Ulamog is put into a graveyard from anywhere, its owner shuffles their graveyard into their library.

Saw It Coming

Counter target spell.
Foretell {1}{U} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Fist of Suns

You may pay {W}{U}{B}{R}{G} rather than pay the mana cost for spells you cast.

Bloodboil Sorcerer

When this creature enters, you take the initiative.
Crown of Madness — {1}{R}, Sacrifice an artifact or creature: Goad target creature. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)

Plains

Mistmeadow Witch

{2}{W}{U}: Exile target creature. Return that card to the battlefield under its owner's control at the beginning of the next end step.

Titanic Ultimatum

Until end of turn, creatures you control get +5/+5 and gain first strike, trample, and lifelink.

Yarok, the Desecrated

Deathtouch, lifelink
If a permanent entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Simic Guildgate

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

Open the Gates

Search your library for a basic land card or Gate card, reveal it, put it into your hand, then shuffle.

Rakdos Signet

Goliath Paladin

Vigilance
When this creature enters, you take the initiative.

Izzet Signet

Undercellar Sweep

When this enchantment enters, you take the initiative.
Whenever you attack, if you or a player you're attacking has the initiative, you create two 1/1 white Soldier creature tokens that are tapped and attacking.

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 token: Add one mana of any color.")

Emiel the Blessed

{3}: Exile another target creature you control, then return it to the battlefield under its owner's control.
Whenever another creature you control enters, you may pay {G/W}. If you do, put a +1/+1 counter on it. If it's a Unicorn, put two +1/+1 counters on it instead. ({G/W} can be paid with either {G} or {W}.)

Cliffgate

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

Azorius Signet

Rakdos Guildgate

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

Reshape the Earth

Search your library for up to ten land cards, put them onto the battlefield tapped, then shuffle.

Arcane Signet

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

Tomb of Horrors Adventurer

When this creature enters, you take the initiative.
Whenever you cast your second spell each turn, copy it. If you've completed a dungeon, copy that spell twice instead. You may choose new targets for the copies. (A copy of a permanent spell becomes a token.)

Black Dragon Gate

This land enters tapped.
As this land enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

Undermountain Adventurer

Vigilance
When this creature enters, you take the initiative.
{T}: Add {G}{G}. If you've completed a dungeon, add six {G} instead.

Sol Ring

Kenrith, the Returned King

{R}: All creatures gain trample and haste until end of turn.
{1}{G}: Put a +1/+1 counter on target creature.
{2}{W}: Target player gains 5 life.
{3}{U}: Target player draws a card.
{4}{B}: Put target creature card from a graveyard onto the battlefield under its owner's control.

Jodah, Archmage Eternal

Flying
You may pay {W}{U}{B}{R}{G} rather than pay the mana cost for spells you cast.

Avenging Hunter

Trample
When this creature enters, you take the initiative.

Izzet Guildgate

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

Kozilek, the Great Distortion

When you cast this spell, if you have fewer than seven cards in hand, draw cards equal to the difference.
Menace
Discard a card with mana value X: Counter target spell with mana value X.