Eaten by Piranhas

Flash
Enchant creature
Enchanted creature loses all abilities and is a black Skeleton creature with base power and toughness 1/1. (It loses all other card types and creature types.)

Displacement Wave

Return all nonland permanents with mana value X or less to their owners' hands.

Renegade Doppelganger

Whenever another creature enters the battlefield under your control, you may have Renegade Doppelganger become a copy of that creature until end of turn. (If it does, it loses this ability for the rest of the turn.)

Quasiduplicate

Create a token that's a copy of target creature you control.
Jump-start (You may cast this card from your graveyard by discarding a card in addition to paying its other costs. Then exile this card.)

Mirror Mockery

Enchant creature
Whenever enchanted creature attacks, you may create a token that's a copy of that creature. Exile that token at end of combat.

Misleading Signpost

Flash
When Misleading Signpost enters the battlefield during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.)
{T}: Add {U}.

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.)

War Room

{T}: Add {C}.
{3}, {T}, Pay life equal to the number of colors in your commanders' color identity: Draw a card.

Endless Evil

Enchant creature you control
At the beginning of your upkeep, create a token that's a copy of enchanted creature, except the token is 1/1.
When enchanted creature dies, if that creature was a Horror, return Endless Evil to its owner's hand.

Dance of Many

When Dance of Many enters the battlefield, create a token that's a copy of target nontoken creature.
When Dance of Many leaves the battlefield, exile the token.
When the token leaves the battlefield, sacrifice Dance of Many.
At the beginning of your upkeep, sacrifice Dance of Many unless you pay {U}{U}.

Thought Vessel

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

Dust Bowl

{T}: Add {C}.
{3}, {T}, Sacrifice a land: Destroy target nonbasic land.

Ornithopter of Paradise

Leyline of Singularity

If Leyline of Singularity is in your opening hand, you may begin the game with it on the battlefield.
All nonland permanents are legendary.

Declaration of Naught

As Declaration of Naught enters the battlefield, choose a card name.
{U}: Counter target spell with the chosen name.

Tribute Mage

When Tribute Mage enters the battlefield, you may search your library for an artifact card with mana value 2, reveal that card, put it into your hand, then shuffle.

Flesh Duplicate

You may have Flesh Duplicate enter the battlefield as a copy of any creature on the battlefield, except it has vanishing 3 if that creature doesn't have vanishing. (A permanent with vanishing 3 enters the battlefield with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)

Mystic Remora

Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Whenever an opponent casts a noncreature spell, you may draw a card unless that player pays {4}.

Rhystic Study

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

Island

Worn Powerstone

Worn Powerstone enters the battlefield tapped.
{T}: Add {C}{C}.

Braids, Conjurer Adept

At the beginning of each player's upkeep, that player may put an artifact, creature, or land card from their hand onto the battlefield.

Mirror Image

You may have Mirror Image enter the battlefield as a copy of a creature you control.

Cyber Conversion

Turn target creature face down. It's a 2/2 Cyberman artifact creature.

Arcane Lighthouse

{T}: Add {C}.
{1}, {T}: Until end of turn, creatures your opponents control lose hexproof and shroud and can't have hexproof or shroud.

Fated Infatuation

Create a token that's a copy of target creature you control. If it's your turn, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Tectonic Edge

{T}: Add {C}.
{1}, {T}, Sacrifice Tectonic Edge: Destroy target nonbasic land. Activate only if an opponent controls four or more lands.

Clever Impersonator

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

Mirage Mockery

Choose one —
• Create a token that's a copy of target artifact creature you control.
• Create a token that's a copy of target nonartifact creature you control.
Entwine {2}{U} (Choose both if you pay the entwine cost.)

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.

Solemn Simulacrum

When Solemn Simulacrum enters the battlefield, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When Solemn Simulacrum dies, you may draw a card.

Engulf the Shore

Return to their owners' hands all creatures with toughness less than or equal to the number of Islands you control.

Apprentice Wizard

Phantasmal Image

You may have Phantasmal Image enter the battlefield as a copy of any creature on the battlefield, except it's an Illusion in addition to its other types and it has "When this creature becomes the target of a spell or ability, sacrifice it."

Arcane Signet

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

Windfall

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.

Kairi, the Swirling Sky

Flying, ward {3}
When Kairi, the Swirling Sky dies, choose one —
• Return any number of target nonland permanents with total mana value 6 or less to their owners' hands.
• Mill six cards, then return up to two instant and/or sorcery cards from your graveyard to your hand.

Blade of Shared Souls

For Mirrodin! (When this Equipment enters the battlefield, create a 2/2 red Rebel creature token, then attach this to it.)
Whenever Blade of Shared Souls becomes attached to a creature, for as long as Blade of Shared Souls remains attached to it, you may have that creature become a copy of another target creature you control.
Equip {2}

Counterspell

Cackling Counterpart

Create a token that's a copy of target creature you control.
Flashback {5}{U}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Aetherize

Return all attacking creatures to their owner's hand.

Buried Ruin

{T}: Add {C}.
{2}, {T}, Sacrifice Buried Ruin: Return target artifact card from your graveyard to your hand.

Phyrexian Metamorph

({U/P} can be paid with either {U} or 2 life.)
You may have Phyrexian Metamorph enter the battlefield as a copy of any artifact or creature on the battlefield, except it's an artifact in addition to its other types.

Vizier of Many Faces

You may have Vizier of Many Faces enter the battlefield as a copy of any creature on the battlefield, except if Vizier of Many Faces was embalmed, the token has no mana cost, it's white, and it's a Zombie in addition to its other types.
Embalm {3}{U}{U}

Silver Myr

Mirrorpool

Mirrorpool enters the battlefield tapped.
{T}: Add {C}.
{2}{C}, {T}, Sacrifice Mirrorpool: Copy target instant or sorcery spell you control. You may choose new targets for the copy.
{4}{C}, {T}, Sacrifice Mirrorpool: Create a token that's a copy of target creature you control.

Pit of Offerings

Pit of Offerings enters the battlefield tapped.
When Pit of Offerings enters the battlefield, exile up to three target cards from graveyards.
{T}: Add {C}.
{T}: Add one mana of any of the exiled cards' colors.

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.")

Gigantoplasm

You may have Gigantoplasm enter the battlefield as a copy of any creature on the battlefield, except it has "{X}: This creature has base power and toughness X/X."

Trophy Mage

When Trophy Mage enters the battlefield, you may search your library for an artifact card with mana value 3, reveal it, put it into your hand, then shuffle.

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

Myriad Landscape

Myriad Landscape enters the battlefield tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

Followed Footsteps

Enchant creature
At the beginning of your upkeep, create a token that's a copy of enchanted creature.

Aetherspouts

For each attacking creature, its owner puts it on the top or bottom of their library.

March of the Machines

Each noncreature artifact is an artifact creature with power and toughness each equal to its mana value. (Equipment that's a creature can't equip a creature.)

Cryptoplasm

At the beginning of your upkeep, you may have Cryptoplasm become a copy of another target creature, except it has this ability.

See Double

This spell can't be copied.
Choose one. If an opponent has eight or more cards in their graveyard, you may choose both.
• Copy target spell. You may choose new targets for the copy. (A copy of a permanent spell becomes a token.)
• Create a token that's a copy of target creature.

Three Steps Ahead

Spree (Choose one or more additional costs.)
+ {1}{U} — Counter target spell.
+ {3} — Create a token that's a copy of target artifact or creature you control.
+ {2} — Draw two cards, then discard a card.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Demolition Field

{T}: Add {C}.
{2}, {T}, Sacrifice Demolition Field: Destroy target nonbasic land an opponent controls. That land's controller may search their library for a basic land card, put it onto the battlefield, then shuffle. You may search your library for a basic land card, put it onto the battlefield, then shuffle.

Glasspool Shore

Glasspool Shore enters the battlefield tapped.
{T}: Add {U}.

Glasspool Mimic

You may have Glasspool Mimic enter the battlefield as a copy of a creature you control, except it's a Shapeshifter Rogue in addition to its other types.

Glasspool Mimic // Glasspool Shore

Maze of Ith

{T}: Untap target attacking creature. Prevent all combat damage that would be dealt to and dealt by that creature this turn.

Mimic Vat

Imprint — Whenever a nontoken creature dies, you may exile that card. If you do, return each other card exiled with Mimic Vat to its owner's graveyard.
{3}, {T}: Create a token that's a copy of a card exiled with Mimic Vat. It gains haste. Exile it at the beginning of the next end step.

Negate

Extravagant Replication

At the beginning of your upkeep, create a token that's a copy of another target nonland permanent you control.

Detection Tower

{T}: Add {C}.
{1}, {T}: Until end of turn, your opponents and creatures your opponents control with hexproof can be the targets of spells and abilities you control as though they didn't have hexproof.

Keiga, the Tide Star

Flying
When Keiga, the Tide Star dies, gain control of target creature.

Ghost Quarter

{T}: Add {C}.
{T}, Sacrifice Ghost Quarter: Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Jace's Archivist

{U}, {T}: Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.

Stunt Double

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

Mirage Mirror

{2}: Mirage Mirror becomes a copy of target artifact, creature, enchantment, or land until end of turn.

Scavenger Grounds

{T}: Add {C}.
{2}, {T}, Sacrifice a Desert: Exile all graveyards.

Visage Bandit

You may have Visage Bandit enter the battlefield as a copy of a creature you control, except it's a Shapeshifter Rogue in addition to its other types.
Plot {2}{U} (You may pay {2}{U} and exile this card from your hand. Cast it as a sorcery on a later turn without paying its mana cost. Plot only as a sorcery.)

Undercover Operative

You may have Undercover Operative enter the battlefield as a copy of any creature on the battlefield, except it enters with a shield counter on it if you control that creature. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

Rapid Hybridization

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

Stoic Sphinx

Flash
Flying
Stoic Sphinx has hexproof as long as you haven't cast a spell this turn.

Court of Vantress

When Court of Vantress enters the battlefield, you become the monarch.
At the beginning of your upkeep, choose up to one other target enchantment or artifact. If you're the monarch, you may create a token that's a copy of it. If you're not the monarch, you may have Court of Vantress become a copy of it, except it has this ability.

Ghastly Mimicry

Enchant creature
At the beginning of your upkeep, create a token that's a copy of enchanted creature, except it's a Spirit in addition to its other types.
If Ghastly Mimicry would be put into a graveyard from anywhere, exile it instead.

Mirrorhall Mimic

You may have Mirrorhall Mimic enter the battlefield as a copy of any creature on the battlefield, except it's a Spirit in addition to its other types.
Disturb {3}{U}{U} (You may cast this card from your graveyard transformed for its disturb cost.)

Mirrorhall Mimic // Ghastly Mimicry

Fabricate

Search your library for an artifact card, reveal it, put it into your hand, then shuffle.

Palladium Myr

High Market

{T}: Add {C}.
{T}, Sacrifice a creature: You gain 1 life.

Sceptre of Eternal Glory

{T}: Add one mana of any color.
{T}: Add three mana of any one color. Activate only if you control three or more lands with the same name.

Clone

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

Blade of Selves

Equipped creature has myriad. (Whenever it attacks, for each opponent other than defending player, you may create a token that's a copy of that creature that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Equip {4}

Stolen Identity

Create a token that's a copy of target artifact or creature.
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.)

Evacuation

Return all creatures to their owners' hands.

Pongify

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

Sol Ring

Bribery

Search target opponent's library for a creature card and put that card onto the battlefield under your control. Then that player shuffles.

Imprisoned in the Moon

Enchant creature, land, or planeswalker
Enchanted permanent is a colorless land with "{T}: Add {C}" and loses all other card types and abilities.

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.

Day's Undoing

Each player shuffles their hand and graveyard into their library, then draws seven cards. If it's your turn, end the turn. (Exile all spells and abilities from the stack, including this card. Discard down to your maximum hand size. Damage wears off, and "this turn" and "until end of turn" effects end.)

Academy Ruins

{T}: Add {C}.
{1}{U}, {T}: Put target artifact card from your graveyard on top of your library.