Nimble Obstructionist

Flash
Flying
Cycling {2}{U} ({2}{U}, Discard this card: Draw a card.)
When you cycle Nimble Obstructionist, counter target activated or triggered ability you don't control.

Phantom Steed

Flash
When Phantom Steed enters the battlefield, exile another target creature you control until Phantom Steed leaves the battlefield.
Whenever Phantom Steed attacks, create a tapped and attacking token that's a copy of the exiled card, except it's an Illusion in addition to its other types. Sacrifice that token at end of combat.

Barrowin of Clan Undurr

When Barrowin of Clan Undurr enters the battlefield, venture into the dungeon. (Enter the first room or advance to the next room.)
Whenever Barrowin of Clan Undurr 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.

Lurching Rotbeast

Cycling {B} ({B}, Discard this card: Draw a card.)

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.

Windcaller Aven

Flying
Cycling {U} ({U}, Discard this card: Draw a card.)
When you cycle Windcaller Aven, target creature gains flying until end of turn.

Atla Palani, Nest Tender

{2}, {T}: Create a 0/1 green Egg creature token with defender.
Whenever an Egg you control dies, reveal cards from the top of your library until you reveal a creature card. Put that card onto the battlefield and the rest on the bottom of your library in a random order.

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.

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.)

Hama Pashar, Ruin Seeker

Room abilities of dungeons you own trigger an additional time.

Horror of the Broken Lands

Whenever you cycle or discard another card, Horror of the Broken Lands gets +2/+1 until end of turn.
Cycling {B} ({B}, Discard this card: Draw a card.)

Herald of the Forgotten

Flying
When Herald of the Forgotten enters the battlefield, if you cast it, return any number of target permanent cards with cycling abilities from your graveyard to the battlefield.

Sarevok's Tome

When Sarevok's Tome enters the battlefield, 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.

Curator of Mysteries

Flying
Whenever you cycle or discard another card, scry 1.
Cycling {U} ({U}, Discard this card: Draw a card.)

Ravenloft Adventurer

When Ravenloft Adventurer enters the battlefield, you take the initiative.
If a creature an opponent controls would die, instead exile it and put a hit counter on it.
Whenever Ravenloft Adventurer 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.

Vile Manifestation

Vile Manifestation gets +1/+0 for each card with cycling in your graveyard.
Cycling {2} ({2}, Discard this card: Draw a card.)

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.)

Unmarked Grave

Search your library for a nonlegendary card, put that card into your graveyard, then shuffle.

Tortured Existence

{B}, Discard a creature card: Return target creature card from your graveyard to your hand.

Sun Titan

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

Striped Riverwinder

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Cycling {U} ({U}, Discard this card: Draw a card.)

Abandoned Sarcophagus

You may cast spells that have a cycling ability from your graveyard.
If a card that has a cycling ability would be put into your graveyard from anywhere and it wasn't cycled, exile it instead.

Triumphant Adventurer

Deathtouch
As long as it's your turn, Triumphant Adventurer has first strike.
Whenever Triumphant Adventurer attacks, venture into the dungeon. (Enter the first room or advance to the next room.)

Imposing Vantasaur

Vigilance
Cycling {1} ({1}, Discard this card: Draw a card.)

Crystalline Resonance

Whenever you cycle a card, you may have Crystalline Resonance become a copy of another target permanent until your next turn, except it has this ability.

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.)

Architects of Will

When Architects of Will enters the battlefield, look at the top three cards of target player's library, then put them back in any order.
Cycling {U/B} ({U/B}, Discard this card: Draw a card.)

Astral Slide

Whenever a player cycles a card, you may exile target creature. If you do, return that card to the battlefield under its owner's control at the beginning of the next end step.

Street Wraith

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Cycling—Pay 2 life. (Pay 2 life, Discard this card: Draw a card.)

Winged Shepherd

Flying, vigilance
Cycling {W} ({W}, Discard this card: Draw a card.)

Eternal Dragon

Flying
{3}{W}{W}: Return Eternal Dragon from your graveyard to your hand. Activate only during your upkeep.
Plainscycling {2} ({2}, Discard this card: Search your library for a Plains card, reveal it, put it into your hand, then shuffle.)

Alhammarret's Archive

If you would gain life, you gain twice that much life instead.
If you would draw a card except the first one you draw in each of your draw steps, draw two cards instead.

Nadaar, Selfless Paladin

Vigilance
Whenever Nadaar, Selfless Paladin enters the battlefield 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.

Acererak the Archlich

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

Drannith Healer

Whenever you cycle another card, you gain 1 life.
Cycling {1} ({1}, Discard this card: Draw a card.)

Astral Drift

Whenever you cycle Astral Drift or cycle another card while Astral Drift is on the battlefield, you may exile target creature. If you do, return that card to the battlefield under its owner's control at the beginning of the next end step.
Cycling {2}{W} ({2}{W}, Discard this card: Draw a card.)

Geier Reach Sanitarium

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

Angel of the Ruins

Flying
When Angel of the Ruins enters the battlefield, exile up to two target artifacts and/or enchantments.
Plainscycling {2} ({2}, Discard this card: Search your library for a Plains card, reveal it, put it into your hand, then shuffle.)

Fates' Reversal

Return up to one target creature card from your graveyard to your hand. Venture into the dungeon. (Enter the first room or advance to the next room.)

Songs of the Damned

Add {B} for each creature card in your graveyard.

Dungeon Delver

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

Tomb of Horrors Adventurer

When Tomb of Horrors Adventurer enters the battlefield, 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.)

Fluctuator

Cycling abilities you activate cost up to {2} less to activate.

Timeless Dragon

Flying
Plainscycling {2} ({2}, Discard this card: Search your library for a Plains card, reveal it, put it into your hand, then shuffle.)
Eternalize {2}{W}{W} ({2}{W}{W}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a 4/4 black Zombie Dragon with no mana cost. Eternalize only as a sorcery.)

Karmic Guide

Flying, protection from black
Echo {3}{W}{W} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When Karmic Guide enters the battlefield, return target creature card from your graveyard to the battlefield.

Rilsa Rael, Kingpin

Deathtouch
When Rilsa Rael, Kingpin enters the battlefield, 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.

Radiant Solar

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

Flourishing Fox

Whenever you cycle another card, put a +1/+1 counter on Flourishing Fox.
Cycling {1} ({1}, Discard this card: Draw a card.)

Doom Whisperer

Flying, trample
Pay 2 life: Surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Storm of Souls

Return all creature cards from your graveyard to the battlefield. Each of them is a 1/1 Spirit with flying in addition to its other types. Exile Storm of Souls.

Aminatou, the Fateshifter

+1: Draw a card, then put a card from your hand on top of your library.
−1: Exile another target permanent you own, then return it to the battlefield under your control.
−6: Choose left or right. Each player gains control of all nonland permanents other than Aminatou, the Fateshifter controlled by the next player in the chosen direction.
Aminatou, the Fateshifter can be your commander.

Glassdust Hulk

Whenever another artifact enters the battlefield under your control, Glassdust Hulk gets +1/+1 until end of turn and can't be blocked this turn.
Cycling {W/U} ({W/U}, Discard this card: Draw a card.)

River Serpent

River Serpent can't attack unless there are five or more cards in your graveyard.
Cycling {U} ({U}, Discard this card: Draw a card.)

New Perspectives

When New Perspectives enters the battlefield, draw three cards.
As long as you have seven or more cards in hand, you may pay {0} rather than pay cycling costs.

Escape Protocol

Whenever you cycle a card, you may pay {1}. When you do, exile target artifact or creature you control, then return it to the battlefield under its owner's control.

Seasoned Dungeoneer

When Seasoned Dungeoneer enters the battlefield, 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.)

White Plume Adventurer

When White Plume Adventurer enters the battlefield, 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.

Teferi's Ageless Insight

If you would draw a card except the first one you draw in each of your draw steps, draw two cards instead.