Room abilities of dungeons you own trigger an additional time.

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

{1}, {T}: Add {W}{U}.

Indestructible {T}: Add one mana of any color.

When Mana Geode enters the battlefield, scry 1. {T}: Add one mana of any color.

{T}: Add {C}. {T}: Add {W} or {U}. Talisman of Progress deals 1 damage to you.

You have no maximum hand size. {T}: Add {C}.

You may have Clever Impersonator enter the battlefield as a copy of any nonland permanent on the battlefield.

You may have Clone enter the battlefield as a copy of any creature on the battlefield.

Flash Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom of your library in a random order.) You may have Sakashima's Protege enter the battlefield as a copy of any permanent that entered the battlefield this turn.

You may have Spark Double enter the battlefield as a copy of a creature or planeswalker you control, except it enters with an additional +1/+1 counter on it if it's a creature, it enters with an additional loyalty counter on it if it's a planeswalker, and it isn't legendary.

Flash You may have Stunt Double enter the battlefield as a copy of any creature on the battlefield.

As Vesuvan Shapeshifter enters the battlefield or is turned face up, you may choose another creature on the battlefield. If you do, until Vesuvan Shapeshifter is turned face down, it becomes a copy of that creature, except it has "At the beginning of your upkeep, you may turn this creature face down." Morph {1}{U}

Destroy target creature. It can't be regenerated. That creature's controller creates a 3/3 green Frog Lizard creature token.

Counter target spell. Untap up to four lands.

When Spine of Ish Sah enters the battlefield, destroy target permanent. When Spine of Ish Sah is put into a graveyard from the battlefield, return Spine of Ish Sah to its owner's hand.

Flying When Aarakocra Sneak enters the battlefield, you take the initiative.

Vigilance If a permanent entering the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time. Permanents entering the battlefield don't cause abilities of permanents your opponents control to trigger.

When Feywild Caretaker enters the battlefield, 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.

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.)

Whenever another nontoken creature enters the battlefield under your control, if it wasn't cast, create a token that's a copy of that creature, except it's a 0/1 white Illusion. {1}{W}, Sacrifice five Illusions: Exile target nonland permanent.

When Priest of Ancient Lore enters the battlefield, you gain 1 life and draw a card.

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

Indestructible As long as your devotion to blue is less than five, Thassa isn't a creature. At the beginning of your end step, exile up to one other target creature you control, then return that card to the battlefield under your control. {3}{U}: Tap another target creature.

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.)

Enchant creature Enchanted creature can't be blocked. Whenever enchanted creature attacks, scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

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

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

Exile up to two target creatures you control, then return those cards to the battlefield under their owner's control.

When Felidar Guardian enters the battlefield, you may exile another target permanent you control, then return that card to the battlefield under its owner's control.

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

When Archaeomancer enters the battlefield, return target instant or sorcery card from your graveyard to your hand.

Exile any number of target creatures you control. Return those cards to the battlefield under their owner's control at the beginning of the next end step.

{T}: Add {C}. {T}: Add {W} or {U}. Adarkar Wastes deals 1 damage to you.

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

Deserted Beach enters the battlefield tapped unless you control two or more other lands. {T}: Add {W} or {U}.

{T}, Pay 1 life, Sacrifice Flooded Strand: Search your library for a Plains or Island card, put it onto the battlefield, then shuffle.

Glacial Fortress enters the battlefield tapped unless you control a Plains or an Island. {T}: Add {W} or {U}.

({T}: Add {W} or {U}.) As Hallowed Fountain enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

({T}: Add {U}.)

({T}: Add {U}.) Mystic Sanctuary enters the battlefield tapped unless you control three or more other Islands. When Mystic Sanctuary enters the battlefield untapped, you may put target instant or sorcery card from your graveyard on top of your library.

({T}: Add {W}.)

({T}: Add {W} or {U}.) Prairie Stream enters the battlefield tapped unless you control two or more basic lands.

You have no maximum hand size. {T}: Add {C}.

{T}: Add {C}. {4}, {T}: Target creature can't be blocked this turn.

{T}: Prevent the next 1 damage that would be dealt to any target this turn. {T}: Target creature can't be blocked this turn.

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.) Equip {1}

Until your next turn, your life total can't change and you gain protection from everything. All permanents you control phase out. (While they're phased out, they're treated as though they don't exist. They phase in before you untap during your untap step.) Exile Teferi's Protection.

Basalt Monolith doesn't untap during your untap step. {T}: Add {C}{C}{C}. {3}: Untap Basalt Monolith.

Flying When Peregrine Drake enters the battlefield, untap up to five lands.

{T}: Add {C}{C}.

If this spell was cast from your hand and you've cast another spell named Approach of the Second Sun this game, you win the game. Otherwise, put Approach of the Second Sun into its owner's library seventh from the top and you gain 7 life.

Destroy all creatures and all permanents attached to creatures.

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

When Cloister Gargoyle enters the battlefield, venture into the dungeon. (Enter the first room or advance to the next room.) As long as you've completed a dungeon, Cloister Gargoyle gets +3/+0 and has flying.

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.)

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

Flying When Eccentric Apprentice enters the battlefield, 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.

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.)

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.)

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.

Flying Whenever Planar Ally attacks, venture into the dungeon. (Enter the first room or advance to the next room.)

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.

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