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.

Merfolk Windrobber

Flying
Whenever Merfolk Windrobber deals combat damage to a player, that player mills a card. (They put the top card of their library into their graveyard.)
Sacrifice Merfolk Windrobber: Draw a card. Activate only if an opponent has eight or more cards in their graveyard.

Quick Study

Arcbound Slith

Whenever Arcbound Slith deals combat damage to a player, put a +1/+1 counter on it.
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

Aetherize

Return all attacking creatures to their owner's hand.

Island

Prosperous Thief

Ninjutsu {1}{U} ({1}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever one or more Ninja or Rogue creatures you control deal combat damage to a player, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Wash Out

Return all permanents of the color of your choice to their owners' hands.

Acquisition Octopus

Whenever Acquisition Octopus or equipped creature deals combat damage to a player, draw a card.
Reconfigure {2} ({2}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)

Moonblade Shinobi

Ninjutsu {2}{U} ({2}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Moonblade Shinobi deals combat damage to a player, create a 1/1 blue Illusion creature token with flying.

Slith Strider

Whenever Slith Strider becomes blocked, draw a card.
Whenever Slith Strider deals combat damage to a player, put a +1/+1 counter on it.

Daze

You may return an Island you control to its owner's hand rather than pay this spell's mana cost.
Counter target spell unless its controller pays {1}.

Rogue's Passage

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

Smuggler's Buggy

Hideaway 4 (When this artifact enters, look at the top four cards of your library, exile one face down, then put the rest on the bottom in a random order.)
Whenever Smuggler's Buggy deals combat damage to a player, you may cast the exiled card without paying its mana cost. If you do, return Smuggler's Buggy to its owner's hand.
Crew 2

Skyship Plunderer

Flying
Whenever Skyship Plunderer deals combat damage to a player, for each kind of counter on target permanent or player, give that permanent or player another counter of that kind.

Trickster's Talisman

Invoke Duplicity — Equipped creature gets +1/+1 and has "Whenever this creature deals combat damage to a player, you may sacrifice Trickster's Talisman. If you do, create a token that's a copy of this creature."
Equip {2}

Counterspell

Reconnaissance Mission

Whenever a creature you control deals combat damage to a player, you may draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

Fell Flagship

Pirates you control get +1/+0.
Whenever Fell Flagship deals combat damage to a player, that player discards a card.
Crew 3 (Tap any number of creatures you control with total power 3 or more: This Vehicle becomes an artifact creature until end of turn.)

Escape Tunnel

{T}, Sacrifice Escape Tunnel: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
{T}, Sacrifice Escape Tunnel: Target creature with power 2 or less can't be blocked this turn.

Dispel

Thousand-Faced Shadow

Ninjutsu {2}{U}{U} ({2}{U}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Flying
When Thousand-Faced Shadow enters from your hand, if it's attacking, create a token that's a copy of another target attacking creature. The token enters tapped and attacking.

Consider

Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Draw a card.

Ruination Guide

Devoid (This card has no color.)
Ingest (Whenever this creature deals combat damage to a player, that player exiles the top card of their library.)
Other colorless creatures you control get +1/+0.

Covert Technician

Ninjutsu {1}{U} ({1}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Covert Technician deals combat damage to a player, you may put an artifact card with mana value less than or equal to that damage from your hand onto the battlefield.

Thought Vessel

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

Jhessian Thief

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Jhessian Thief deals combat damage to a player, draw a card.

March of Swirling Mist

As an additional cost to cast this spell, you may exile any number of blue cards from your hand. This spell costs {2} less to cast for each card exiled this way.
Up to X target creatures phase out. (While they're phased out, they're treated as though they don't exist. Each one phases in before its controller untaps during their next untap step.)

Terrain Generator

{T}: Add {C}.
{2}, {T}: You may put a basic land card from your hand onto the battlefield tapped.

Lu Xun, Scholar General

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
Whenever Lu Xun, Scholar General deals damage to an opponent, you may draw a card.

Zephyr Boots

Equipped creature has flying.
Whenever equipped creature deals combat damage to a player, draw a card, then discard a card.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Herald of Hoofbeats

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
Other Knights you control have horsemanship.

Thassa's Emissary

Bestow {5}{U} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Whenever Thassa's Emissary or enchanted creature deals combat damage to a player, draw a card.
Enchanted creature gets +3/+3.

Sun Quan, Lord of Wu

Creatures you control have horsemanship. (They can't be blocked except by creatures with horsemanship.)

Riptide Pilferer

Whenever Riptide Pilferer deals combat damage to a player, that player discards a card.
Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Arcane Signet

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

Salvage Drone

Devoid (This card has no color.)
Ingest (Whenever this creature deals combat damage to a player, that player exiles the top card of their library.)
When Salvage Drone dies, you may draw a card. If you do, discard a card.

Nimble Brigand

Nimble Brigand can't be blocked if you've committed a crime this turn. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)
Whenever Nimble Brigand deals combat damage to a player, draw a card.

Cybership

Flying
Whenever Cybership deals combat damage to a player, put the top two cards of that player's library onto the battlefield face down under your control. They're 2/2 Cyberman artifact creatures.
Crew 4

Perplexing Test

Choose one —
• Return all creature tokens to their owners' hands.
• Return all nontoken creatures to their owners' hands.

Hands of Binding

Tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Piper Wright, Publick Reporter

Whenever Piper Wright deals combat damage to a player, investigate that many times. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
Whenever you sacrifice a Clue, put a +1/+1 counter on target creature you control.

Promising Vein

{T}: Add {C}.
{1}, {T}, Sacrifice Promising Vein: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

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.)

Sol Ring

Mistway Spy

Flying
Disguise {1}{U} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)
When Mistway Spy is turned face up, until end of turn, whenever a creature you control deals combat damage to a player, investigate.

Goggles of Night

Whenever equipped creature deals combat damage to a player, scry 1, then draw a card. (To scry 1, look at the top card of your library, then you may put that card on the bottom.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Reliquary Tower

Mist Intruder

Devoid (This card has no color.)
Flying
Ingest (Whenever this creature deals combat damage to a player, that player exiles the top card of their library.)

Bladegriff Prototype

Flying
Whenever Bladegriff Prototype deals combat damage to a player, destroy target nonland permanent of that player's choice that one of your opponents controls.

Thrummingbird

Flying
Whenever Thrummingbird deals combat damage to a player, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Daring Saboteur

{2}{U}: Daring Saboteur can't be blocked this turn.
Whenever Daring Saboteur deals combat damage to a player, you may draw a card. If you do, discard a card.

Quietus Spike

Equipped creature has deathtouch.
Whenever equipped creature deals combat damage to a player, that player loses half their life, rounded up.
Equip {3}

Geode Golem

Trample
Whenever Geode Golem deals combat damage to a player, you may cast your commander from the command zone without paying its mana cost. (You still pay any additional costs.)

Unsummon

Return target creature to its owner's hand.

Moon-Circuit Hacker

Ninjutsu {U} ({U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Moon-Circuit Hacker deals combat damage to a player, you may draw a card. If you do, discard a card unless Moon-Circuit Hacker entered this turn.

Sturmgeist

Flying
Sturmgeist's power and toughness are each equal to the number of cards in your hand.
Whenever Sturmgeist deals combat damage to a player, draw a card.

Last Thoughts

Draw a card.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Jeskai Elder

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Jeskai Elder deals combat damage to a player, you may draw a card. If you do, discard a card.

Shortcut Seeker

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

Hakka, Whispering Raven

Flying
Whenever Hakka, Whispering Raven deals combat damage to a player, return it to its owner's hand, then scry 2.

Alrund, God of the Cosmos

Alrund gets +1/+1 for each card in your hand and each foretold card you own in exile.
At the beginning of your end step, choose a card type, then reveal the top two cards of your library. Put all cards of the chosen type revealed this way into your hand and the rest on the bottom of your library in any order.

Alrund, God of the Cosmos // Hakka, Whispering Raven

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Gateway Sneak

Whenever a Gate you control enters, Gateway Sneak can't be blocked this turn.
Whenever Gateway Sneak deals combat damage to a player, draw a card.

Evolving Wilds

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

Guild Thief

Whenever Guild Thief deals combat damage to a player, put a +1/+1 counter on it.
Cunning Action — {3}{U}: Guild Thief can't be blocked this turn.

Soulknife Spy

Whenever Soulknife Spy deals combat damage to a player, draw a card.

Foil

You may discard an Island card and another card rather than pay this spell's mana cost.
Counter target spell.

Retraced Image

Reveal a card in your hand, then put that card onto the battlefield if it has the same name as a permanent.

Catlike Curiosity

Enchant creature
Enchanted creature has "Whenever this creature deals combat damage to a player, draw a card."
If Catlike Curiosity would be put into a graveyard from anywhere, exile it instead.

Mischievous Catgeist

Whenever Mischievous Catgeist deals combat damage to a player, draw a card.
Disturb {2}{U} (You may cast this card from your graveyard transformed for its disturb cost.)

Mischievous Catgeist // Catlike Curiosity

Negate

Schema Thief

Flying
Whenever Schema Thief deals combat damage to a player, create a token that's a copy of target artifact that player controls.