Counterspell

Eccentric Apprentice

Flying
When this creature enters, venture into the dungeon. (Enter the first room or advance to the next room.)
At the beginning of combat on your turn, if you've completed a dungeon, up to one target creature becomes a Bird with base power and toughness 1/1 and flying until end of turn.

Secret Door

Defender
{4}{U}: Venture into the dungeon. Activate only as a sorcery. (Enter the first room or advance to the next room.)

Dungeon of the Mad Mage

Yawning Portal — You gain 1 life. (Leads to: Dungeon Level)
Dungeon Level — Scry 1. (Leads to: Goblin Bazaar, Twisted Caverns)
Goblin Bazaar — Create a Treasure token. (Leads to: Lost Level)
Twisted Caverns — Target creature can't attack until your next turn. (Leads to: Lost Level)
Lost Level — Scry 2. (Leads to: Runestone Caverns, Muiral's Graveyard)
Runestone Caverns — Exile the top two cards of your library. You may play them. (Leads to: Deep Mines)
Muiral's Graveyard — Create two 1/1 black Skeleton creature tokens. (Leads to: Deep Mines)
Deep Mines — Scry 3. (Leads to: Mad Wizard's Lair)
Mad Wizard's Lair — Draw three cards and reveal them. You may cast one of them without paying its mana cost.

Dictate of the Twin Gods

Flash
If a source would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Mountain

Gratuitous Violence

If a creature you control would deal damage to a permanent or player, it deals double that damage instead.

Sol Ring

Bane's Invoker

Wind Walk — {8}: Up to two target creatures each get +2/+2 and gain flying until end of turn.

Ishai, Ojutai Dragonspeaker

Flying
Whenever an opponent casts a spell, put a +1/+1 counter on Ishai.
Partner (You can have two commanders if both have partner.)

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.)

Faerie Mastermind

Flash
Flying
Whenever an opponent draws their second card each turn, you draw a card.
{3}{U}: Each player draws a card.

Bar the Gate

Counter target creature or planeswalker spell. Venture into the dungeon. (Enter the first room or advance to the next room.)

Mana Tithe

Counter target spell unless its controller pays {1}.

Mulldrifter

Flying
When this creature enters, draw two cards.
Evoke {2}{U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Island

Dragon

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.)

Dungeon Delver

Commander creatures you own have "Room abilities of dungeons you own trigger an additional time."

Arcane Investigator

Search the Room — {5}{U}: Roll a d20.
1—9 | Draw a card.
10—20 | Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.

Kick in the Door

Put a +1/+1 counter on target creature. That creature gains haste until end of turn and can't be blocked by Walls this turn. Venture into the dungeon. (Enter the first room or advance to the next room.)

Midnight Pathlighter

Creatures you control can't be blocked except by legendary creatures.
Whenever one or more creatures you control deal combat damage to a player, venture into the dungeon. (Enter the first room or advance to the next room.)

Displacer Kitten

Avoidance — Whenever you cast a noncreature spell, exile up to one target nonland permanent you control, then return that card to the battlefield under its owner's control.

Ranger's Hawk

Flying
{3}, {T}, Tap another untapped creature you control: Venture into the dungeon. Activate only as a sorcery. (Enter the first room or advance to the next room.)

Chromatic Lantern

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

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.

Command Tower

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

Jeska, Thrice Reborn

Jeska enters with a loyalty counter on her for each time you've cast a commander from the command zone this game.
0: Choose target creature. Until your next turn, if that creature would deal combat damage to one of your opponents, it deals triple that damage to that player instead.
−X: Jeska deals X damage to each of up to three targets.
Jeska, Thrice Reborn can be your commander.
Partner

Goliath Paladin

Vigilance
When this creature enters, you take the initiative.

Sky Crier

Flying, lifelink
{3}{W}: You and target opponent each draw a card.

Steadfast Unicorn

{3}{W}: Creatures you control get +1/+1 and gain vigilance until end of turn. Activate only during your turn. (Attacking doesn't cause them to tap.)

+2 Mace

Equipped creature gets +2/+2.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Rebuff the Wicked

Counter target spell that targets a permanent you control.

Corridor Monitor

When this creature enters, untap target artifact or creature you control.

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.

Arcane Signet

Aarakocra Sneak

Flying
When this creature enters, you take the initiative.

Displacer Beast

When this creature enters, venture into the dungeon. (Enter the first room or advance to the next room.)
Displacement — {3}{U}: Return this creature to its owner's hand.

Mana Drain

Counter target spell. At the beginning of your next main phase, add an amount of {C} equal to that spell's mana value.

Negate

Hama Pashar, Ruin Seeker

Room abilities of dungeons you own trigger an additional time.

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.

Imoen, Mystic Trickster

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
At the beginning of your end step, if you have the initiative, draw a card. Draw another card if you've completed a dungeon.
Choose a Background (You can have a Background as a second commander.)

Treasure

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

Dungeon Map

{T}: Add {C}.
{3}, {T}: Venture into the dungeon. Activate only as a sorcery. (Enter the first room or advance to the next room.)

Immovable Rod

You may choose not to untap this artifact during your untap step.
Whenever this artifact becomes untapped, venture into the dungeon.
{3}{W}, {T}: For as long as this artifact remains tapped, another target permanent loses all abilities and can't attack or block.

Keen-Eared Sentry

You have hexproof. (You can't be the target of spells or abilities your opponents control.)
Each opponent can't venture into the dungeon more than once each turn.

Far Traveler

Commander creatures you own have "At the beginning of your end step, exile up to one target tapped creature you control, then return it to the battlefield under its owner's control."

Panharmonicon

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

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.")

Yuan-Ti Malison

This creature can't be blocked as long as it's attacking alone.
Whenever this creature deals combat damage to a player, venture into the dungeon. (Enter the first room or advance to the next room.)

Ominous Parcel

{2}, {T}, Sacrifice this artifact: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
{5}, {T}, Sacrifice this artifact: It deals 4 damage to target creature.

Enchant creature
Enchanted creature has flying and "Whenever this creature deals combat damage to a player, venture into the dungeon." (Enter the first room or advance to the next room.)

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.)

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.

Gloom Stalker

As long as you've completed a dungeon, this creature has double strike.

Springjaw Trap

Flash
{4}, {T}, Sacrifice this artifact: It deals 3 damage to any target.

Plains

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.)

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Delver's Torch

Equipped creature gets +1/+1.
Whenever equipped creature attacks, venture into the dungeon. (Enter the first room or advance to the next room.)
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Dungeon Descent

This land enters tapped.
{T}: Add {C}.
{4}, {T}, Tap an untapped legendary creature you control: Venture into the dungeon. Activate only as a sorcery. (Enter the first room or advance to the next room.)

Veteran Dungeoneer

When this creature enters, venture into the dungeon. (Enter the first room or advance to the next room.)

Bronze Walrus

When this creature enters, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)
{T}: Add one mana of any color.

War Screecher

Flying
{5}{W}, {T}: Other creatures you control get +1/+1 until end of turn.

Dragonlord Ojutai

Flying
Dragonlord Ojutai has hexproof as long as it's untapped.
Whenever Dragonlord Ojutai deals combat damage to a player, look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.

The Initiative

Whenever one or more creatures a player controls deal combat damage to you, that player takes the initiative.
Whenever you take the initiative and at the beginning of your upkeep, venture into Undercity. (If you're in a dungeon, advance to the next room. If you're not, enter Undercity. You can take the initiative even if you already have it.)

Have

Undercity

You can't enter this dungeon unless you "venture into Undercity."
Secret Entrance — Search your library for a basic land card, reveal it, put it into your hand, then shuffle. (Leads to: Forge, Lost Well)
Forge — Put two +1/+1 counters on target creature. (Leads to: Trap!, Arena)
Lost Well — Scry 2. (Leads to: Arena, Stash)
Trap! — Target player loses 5 life. (Leads to: Archives)
Arena — Goad target creature. (Leads to: Archives, Catacombs)
Stash — Create a Treasure token. (Leads to: Catacombs)
Archives — Draw a card. (Leads to: Throne of the Dead Three)
Catacombs — Create a 4/1 black Skeleton creature token with menace. (Leads to: Throne of the Dead Three)
Throne of the Dead Three — Reveal the top ten cards of your library. Put a creature card from among them onto the battlefield with three +1/+1 counters on it. It gains hexproof until your next turn. Then shuffle.

Undercity // The Initiative

Frontline Medic

Battalion — Whenever this creature and at least two other creatures attack, creatures you control gain indestructible until end of turn.
Sacrifice this creature: Counter target spell with {X} in its mana cost unless its controller pays {3}.

Witching Well

When this artifact enters, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)
{3}{U}, Sacrifice this artifact: Draw two cards.

Velomachus Lorehold

Flying, vigilance, haste
Whenever Velomachus Lorehold attacks, look at the top seven cards of your library. You may cast an instant or sorcery spell with mana value less than or equal to Velomachus Lorehold's power from among them without paying its mana cost. Put the rest on the bottom of your library in a random order.