Mnemonic Betrayal

Exile all opponents' graveyards. You may cast spells from among those cards this turn, and mana of any type can be spent to cast them. At the beginning of the next end step, if any of those cards remain exiled, return them to their owners' graveyards.
Exile Mnemonic Betrayal.

Dimir Signet

Mother of Goons

Whenever a creature an opponent controls dies, sacrifice Mother of Goons unless you insult that creature.

Gifts Given

Search target opponent's library for four cards with different names and reveal them. That player chooses two of those cards. Put the chosen cards into the player's graveyard and the rest into your hand. Then that player shuffles their library.

Sol Ring

Counterspell

Tainted Isle

{T}: Add {C}.
{T}: Add {U} or {B}. Activate only if you control a Swamp.

Over My Dead Bodies

Creature cards in graveyards can attack and block as though they were on the battlefield, can block or be blocked only by creature cards in graveyards, are Zombies in addition to their other types, and have undeathtouch. (If they would deal damage to a creature card, exile that creature card instead.)
Creature cards in your graveyard have haste.

Johnny, Combo Player

{4}: Search your library for a card, put that card into your hand, then shuffle.

Reliquary Tower

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

Infernal Spawn of Evil

Flying, first strike
{1}{B}, Reveal Infernal Spawn of Evil from your hand, Say "It's coming!": Infernal Spawn of Evil deals 1 damage to target opponent or planeswalker. Activate only during your upkeep and only once each turn.

Jeweled Lotus

{T}, Sacrifice Jeweled Lotus: Add three mana of any one color. Spend this mana only to cast your commander.

Talisman of Dominance

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

Xanathar, Guild Kingpin

At the beginning of your upkeep, choose target opponent. Until end of turn, that player can't cast spells, you may look at the top card of their library any time, you may play the top card of their library, and you may spend mana as though it were mana of any color to cast spells this way.

Graveyard Busybody

All graveyards are also your graveyards.
Graveyard Busybody's power and toughness are each equal to the number of cards with flavor text in your graveyards.

Fierce Guardianship

If you control a commander, you may cast this spell without paying its mana cost.
Counter target noncreature spell.

Rewind

Counter target spell. Untap up to four lands.

Mana Crypt

At the beginning of your upkeep, flip a coin. If you lose the flip, Mana Crypt deals 3 damage to you.
{T}: Add {C}{C}.

Sunken Ruins

{T}: Add {C}.
{U/B}, {T}: Add {U}{U}, {U}{B}, or {B}{B}.

Cyclonic Rift

Return target nonland permanent you don't control to its owner's hand.
Overload {6}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Spell Counter

Counter target spell.
Gotcha — If an opponent says "spell" or "counter," you may say "Gotcha!" When you do, return Spell Counter from your graveyard to your hand.

Clocknapper

When Clocknapper enters, choose beginning phase, first main phase, combat phase, postcombat main phase, or ending phase. Steal that phase from target player during their next turn. (That phase occurs as though it's your turn instead.)

Ancient Tomb

{T}: Add {C}{C}. Ancient Tomb deals 2 damage to you.

Masterful Ninja

Haste
Reveal Masterful Ninja from your hand: Masterful Ninja is on the battlefield and in your hand until end of turn.
{1}{B}: Masterful Ninja gets +1/+1 until end of turn.

Sublime Epiphany

Choose one or more —
• Counter target spell.
• Counter target activated or triggered ability.
• Return target nonland permanent to its owner's hand.
• Create a token that's a copy of target creature you control.
• Target player draws a card.

Hoisted Hireling

Hoisted Hireling has flying as long as it's being held above the battlefield.

Secret Base

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a spell that shares a watermark with Secret Base.

Number Crunch

Return target permanent to its owner's hand.
Gotcha — If an opponent says a number, you may say "Gotcha!" When you do, return Number Crunch from your graveyard to your hand.

Exotic Orchard

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

Shipwreck Marsh

Shipwreck Marsh enters tapped unless you control two or more other lands.
{T}: Add {U} or {B}.

Underdome

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to pay Un-costs.

City of Ass

City of Ass enters tapped.
{T}: Add one and one-half mana of any one color.

Cheatyface

If Cheatyface is in your hand, you may sneak Cheatyface onto the battlefield. If an opponent catches you right away, that player may exile Cheatyface.
Flying

Fowl Play

Enchant creature
Enchanted creature loses all abilities and is a Bird creature with base power and toughness 1/1.

Magic Word

Enchant creature
As Magic Word enters, choose a word.
Whisper the chosen word: Tap enchanted creature.

Baleful Mastery

You may pay {1}{B} rather than pay this spell's mana cost.
If the {1}{B} cost was paid, an opponent draws a card.
Exile target creature or planeswalker.

Notion Thief

Flash
If an opponent would draw a card except the first one they draw in each of their draw steps, instead that player skips that draw and you draw a card.

Arcane Signet

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

Morphic Pool

Morphic Pool enters tapped unless you have two or more opponents.
{T}: Add {U} or {B}.

Entirely Normal Armchair

During your turn, if Entirely Normal Armchair is in your hand, you may hide it on the battlefield.
{0}: Return Entirely Normal Armchair to its owner's hand. Only your opponents may activate this ability and only if they see Entirely Normal Armchair.
{2}, Sacrifice Entirely Normal Armchair: Destroy target attacking creature.

Animate Library

Enchant your library
Enchanted library is an artifact creature on the battlefield with power and toughness each equal to the number of cards in it. It's still a library.
If enchanted library would leave the battlefield, exile Animate Library instead.

Gilded Lotus

Infernal Spawn of Infernal Spawn of Evil

Flying, first strike, trample
Once each turn, while you're searching your library, you may pay {1}{B}, reveal Infernal Spawn of Infernal Spawn of Evil from your library and say "I'm coming, too!" If you do, Infernal Spawn of Infernal Spawn of Evil deals 2 damage to a player of your choice.

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.

Bad Ass

Swamp

Watery Grave

({T}: Add {U} or {B}.)
As Watery Grave enters, you may pay 2 life. If you don't, it enters tapped.

Censorship

As Censorship enters, choose a word.
Whenever a player says the chosen word, Censorship deals 2 damage to that player.

Drowned Catacomb

Drowned Catacomb enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Spy Eye

Flying
Whenever Spy Eye deals combat damage to a player, you may draw a card from that player's library.

As long as X is in X's owner's opponent's hand, X's owner may cast X and activate X's abilities. That opponent can't cast X and plays with their hand revealed.
{U}{B}, {T}: Put X into target opponent's hand.
{3}{U}{B}: You may play a land or cast a spell from the hand X is in. If you cast a spell this way, you cast it without paying its mana cost.

Command Tower

Midnight Clock

{T}: Add {U}.
{2}{U}: Put an hour counter on Midnight Clock.
At the beginning of each upkeep, put an hour counter on Midnight Clock.
When the twelfth hour counter is put on Midnight Clock, shuffle your hand and graveyard into your library, then draw seven cards. Exile Midnight Clock.

City of Brass

Whenever City of Brass becomes tapped, it deals 1 damage to you.
{T}: Add one mana of any color.

Question Elemental?

Did you know this creature has flying?
Are you aware that any time you say something that isn't a question, when a player points out this fact first, they gain control of Question Elemental?

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

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}.)
Sunken Hollow enters tapped unless you control two or more basic lands.

Last-Minute Chopping

Ask target opponent if they remembered to get you a present. If they say yes, they put a card they own from outside the game into your hand. Otherwise, you gain control of target permanent they control.

Thran Dynamo

Common Courtesy

Whenever a player casts a spell without asking your permission while casting it, counter that spell.
When a player asks you permission to cast a spell and you refuse, counter that spell and sacrifice Common Courtesy.

Mana Confluence

{T}, Pay 1 life: Add one mana of any color.

Infernius Spawnington III, Esq.

Flying, first strike, trample, haste
This spell costs {3} less to cast for each card you've revealed this turn.
When Infernius Spawnington III, Esq. enters, you may say "I'm here." If you do, it deals 3 damage to target player.

Mox Amber

{T}: Add one mana of any color among legendary creatures and planeswalkers you control.

Pact of Negation

Counter target spell.
At the beginning of your next upkeep, pay {3}{U}{U}. If you don't, you lose the game.

Bog Humbugs

Flying
Whenever Bog Humbugs deals combat damage, hum that many notes of a festive song. If you can, put a +1/+1 counter on Bog Humbugs.

Mana Vault

Mana Vault doesn't untap during your untap step.
At the beginning of your upkeep, you may pay {4}. If you do, untap Mana Vault.
At the beginning of your draw step, if Mana Vault is tapped, it deals 1 damage to you.
{T}: Add {C}{C}{C}.

Lightning Greaves

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

Demonic Tutor

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

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Sly Spy

Whenever Sly Spy deals combat damage to a player, that player reveals the top card of their library. Put that card into your hand and you lose life equal to its mana value.

Toxic Deluge

As an additional cost to cast this spell, pay X life.
All creatures get -X/-X until end of turn.

Phoebe, Head of S.N.E.A.K.

Phoebe, Head of S.N.E.A.K. can't be blocked by creatures with flavor text.
{2}{U}{B}: Phoebe permanently steals target creature's text box. (That creature loses all rules text, flavor text, and watermarks. This creature gains them.)

Ashiok, Dream Render

Spells and abilities your opponents control can't cause their controller to search their library.
−1: Target player mills four cards. Then exile each opponent's graveyard.

B.O.B. (Bevy of Beebles)

As B.O.B. enters, create four 1/1 blue Beeble creature tokens.
The number of loyalty counters on B.O.B. is equal to the number of Beebles you control. (Create or sacrifice Beebles whenever B.O.B. gains or loses loyalty.)
+1: Up to X target Beebles can't be blocked this turn, where X is the number of cards in your hand.
−1: Draw a card.

Spell Swindle

Counter target spell. Create X Treasure tokens, where X is that spell's mana value. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Bojuka Bog

Bojuka Bog enters tapped.
When Bojuka Bog enters, exile target player's graveyard.
{T}: Add {B}.

Island

Blurry Beeble

Blurry (This creature can be blocked only if defending player was wearing glasses as it was cast.)
Whenever Blurry Beeble deals combat damage to a player, you may draw a card. If you do, discard a card.

Mission Briefing

Surveil 2, then choose an instant or sorcery card in your graveyard. You may cast it this turn. If that spell would be put into your graveyard, exile it instead. (To 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.)

Carnivorous Death-Parrot

Flying
At the beginning of your upkeep, sacrifice Carnivorous Death-Parrot unless you say its flavor text.

Hangman

As Hangman enters, secretly note a word with six to eight letters.
{1}: Target player who doesn't control Hangman guesses the noted word or an unguessed letter in that word. If they guess wrong, put a +1/+1 counter on Hangman. Any player may activate this ability.
When a player guesses the noted word or all of its letters, sacrifice Hangman.

Opposition Agent

Flash
You control your opponents while they're searching their libraries.
While an opponent is searching their library, they exile each card they find. You may play those cards for as long as they remain exiled, and you may spend mana as though it were mana of any color to cast them.