Acererak the Archlich

When Acererak enters, if you haven't completed Tomb of Annihilation, return Acererak to its owner's hand and venture into the dungeon.
Whenever Acererak attacks, for each opponent, you create a 2/2 black Zombie creature token unless that player sacrifices a creature of their choice.

Thorough Investigation

Whenever you attack, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
Whenever you sacrifice a Clue, venture into the dungeon. (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.

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.

Plains

Azorius Signet

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.

Ashen Rider

Flying
When this creature enters or dies, exile target permanent.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Geier Reach Sanitarium

{T}: Add {C}.
{2}, {T}: Each player draws a card, then discards a card.

Arcane Signet

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

Thriving Heath

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

Nadaar, Selfless Paladin

Vigilance
Whenever Nadaar enters or attacks, venture into the dungeon. (Enter the first room or advance to the next room.)
Other creatures you control get +1/+1 as long as you've completed a dungeon.

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.)

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.

Triumphant Adventurer

Deathtouch
During your turn, this creature has first strike.
Whenever this creature attacks, venture into the dungeon. (Enter the first room or advance to the next room.)

Hostile Negotiations

Exile the top three cards of your library in a face-down pile, then exile the top three cards of your library in another face-down pile. Look at the cards in each pile, then turn a pile of your choice face up. An opponent chooses one of those piles. Put that pile into your hand and the other into your graveyard. You lose 3 life.

Thriving Moor

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

Bar the Gate

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

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.)

Sun Titan

Vigilance
Whenever this creature enters or attacks, you may return target permanent card with mana value 3 or less from your graveyard to the battlefield.

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.

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.)

Command Tower

Priest of Fell Rites

{T}, Pay 3 life, Sacrifice this creature: Return target creature card from your graveyard to the battlefield. Activate only as a sorcery.
Unearth {3}{W}{B} ({3}{W}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Talisman of Dominance

{T}: Add {C}.
{T}: Add {U} or {B}. This artifact deals 1 damage to you.

Prairie Stream

({T}: Add {W} or {U}.)
This land enters tapped unless you control two or more basic lands.

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Counterspell

Plaguecrafter

When this creature enters, each player sacrifices a creature or planeswalker of their choice. Each player who can't discards a card.

Exotic Orchard

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

Talisman of Progress

{T}: Add {C}.
{T}: Add {W} or {U}. This artifact deals 1 damage to you.

Choked Estuary

As this land enters, you may reveal an Island or Swamp card from your hand. If you don't, this land enters tapped.
{T}: Add {U} or {B}.

Radiant Solar

Flying, lifelink
Whenever this creature or another nontoken creature you control enters, venture into the dungeon. (Enter the first room or advance to the next room.)
{W}, Discard this card: Venture into the dungeon and you gain 3 life.

Necromantic Selection

Destroy all creatures, then return a creature card put into a graveyard this way to the battlefield under your control. It's a black Zombie in addition to its other colors and types. Exile Necromantic Selection.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

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.

Safana, Calimport Cutthroat

Menace
At the beginning of your end step, if you have the initiative, create a Treasure token. Create three of those tokens instead if you've completed a dungeon.
Choose a Background (You can have a Background as a second commander.)

Arcane Sanctum

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

Wayfarer's Bauble

{2}, {T}, Sacrifice this artifact: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Island

Burnished Hart

{3}, Sacrifice this creature: Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Sunken Hollow

({T}: Add {U} or {B}.)
This land enters tapped unless you control two or more basic lands.

Barrowin of Clan Undurr

When Barrowin enters, venture into the dungeon. (Enter the first room or advance to the next room.)
Whenever Barrowin attacks, return up to one creature card with mana value 3 or less from your graveyard to the battlefield if you've completed a dungeon.

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.)

Sol Ring

Despark

Exile target permanent with mana value 4 or greater.

Oriq Loremage

{T}: Search your library for a card, put it into your graveyard, then shuffle. If it's an instant or sorcery card, put a +1/+1 counter on this creature.

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.

Evolving Wilds

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

Swamp

Orzhov Signet

Thriving Isle

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

Dimir Signet

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.)

Sefris of the Hidden Ways

Whenever one or more creature cards are put into your graveyard from anywhere, venture into the dungeon. This ability triggers only once each turn. (To venture into the dungeon, enter the first room or advance to the next room.)
Create Undead — Whenever you complete a dungeon, return target creature card from your graveyard to the battlefield.

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.)

Hama Pashar, Ruin Seeker

Room abilities of dungeons you own trigger an additional time.

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.)

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.)

Fellwar Stone

Talisman of Hierarchy

{T}: Add {C}.
{T}: Add {W} or {B}. This artifact deals 1 damage to you.

Terramorphic Expanse

Yuan-Ti Fang-Blade

Deathtouch
Whenever this creature deals combat damage to a player, venture into the dungeon. (Enter the first room or advance to the next room.)

Reassembling Skeleton

{1}{B}: Return this card from your graveyard to the battlefield tapped.

Dungeon Delver

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

Port Town

As this land enters, you may reveal a Plains or Island card from your hand. If you don't, this land enters tapped.
{T}: Add {W} or {U}.