Retro-Mutation

Flash
Enchant creature
Enchanted creature is a Turtle with base power and toughness 0/1. It can't attack and loses all abilities. (It also loses all other creature types.)

Continue?

Choose up to four target creature cards in your graveyard that were put there from the battlefield this turn. Return them to the battlefield.

Irma, Part-Time Mutant

At the beginning of combat on your turn, Irma becomes a copy of up to one other target creature you control, except her name is Irma, Part-Time Mutant and she has this ability. Then put a +1/+1 counter on her.

April O'Neil, Live on the Scene

Whenever a Mutant, Ninja, or Turtle you control enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
Partner—Character select

Spire Garden

This land enters tapped unless you have two or more opponents.
{T}: Add {R} or {G}.

Dragonskull Summit

This land enters tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

Grand Coliseum

This land enters tapped.
{T}: Add {C}.
{T}: Add one mana of any color. This land deals 1 damage to you.

The Ooze

Whenever a creature you control with a +1/+1 counter on it leaves the battlefield, create a Mutagen token for each +1/+1 counter on it. (A Mutagen token is an artifact with "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")
{T}: Exile target card from a graveyard. Create a Mutagen token.

Bebop, Skull & Crossbones

Partner with Rocksteady, Mutant Marauder (When this creature enters, target player may put Rocksteady into their hand from their library, then shuffle.)
Deathtouch
Whenever Bebop deals combat damage to a player, you may draw X cards, where X is the number of counters on Bebop. If you do, you lose X life.

Leader's Talent

(Gain the next level as a sorcery to add its ability.)
Whenever you attack, put a +1/+1 counter on target attacking creature.
{2}{W}: Level 2
Whenever a creature you control leaves the battlefield, if it had a counter on it, you gain 2 life.
{3}{W}: Level 3
Whenever you cast a spell, put a +1/+1 counter on each creature you control.

Coin of Mastery

Each creature you control enters with an additional +1/+1 counter on it for each mana from an artifact source spent to cast it.
{T}: Create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Evolving Wilds

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

Mountain

Casey Jones, Back Alley Brute

Menace
Whenever Casey Jones attacks, put a +1/+1 counter on target attacking creature.
Whenever you put one or more +1/+1 counters on a creature you control, Casey Jones deals that much damage to target opponent.

Copy

(This token can be used to represent a token that's a copy of a permanent.)

Super Combo

Replicate {2} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Target creature you control deals damage equal to its power to target creature an opponent controls.

Thriving Isle

This land enters tapped. As it enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Raphael, the Muscle

Double all damage that creatures you control with counters on them would deal.
When Raphael enters, create a Mutagen token.
Partner—Character select (You can have two commanders if both have this ability.)

Michelangelo, Mutant BFF

Each creature you control with a counter on it can't be blocked by more than one creature.
Whenever Michelangelo enters or attacks, create a Mutagen token. (It's an artifact with "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")

Turtle Lair

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a Ninja or Turtle spell.
{3}, {T}: Target Ninja or Turtle can't be blocked this turn.

Fast Forward

This spell costs {1} less to cast for each opponent you attacked this turn.
Goad all creatures your opponents control. (Until your next turn, those creatures attack each combat if able and attack a player other than you if able.)

Vernal Fen

({T}: Add {B} or {G}.)
This land enters tapped unless you control two or more basic lands.

Exploding Barrel

{T}: Add one mana of any color. Put a pressure counter on this artifact.
{8}, {T}, Sacrifice this artifact: It deals 20 damage to target creature. This ability costs {1} less to activate for each pressure counter on this artifact. Activate only as a sorcery.

Shredder, Shadow Master

Whenever Shredder attacks a player, for each other opponent, create a token that's a copy of Shredder tapped and attacking that player, except it isn't legendary. Sacrifice those tokens at end of combat.
Whenever Shredder deals combat damage to a player, that player loses half their life, rounded up.

Knight

Level Up

Enchant creature
When this Aura enters, put a +1/+1 counter on enchanted creature.
Enchanted creature has "Whenever this creature attacks, double the number of +1/+1 counters on it. Then if it has power 10 or greater, draw a card."

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Baxter, Fly in the Ointment

Whenever Baxter enters or attacks, each creature you control with a counter on it gains flying until end of turn.
Whenever you draw a card, put a +1/+1 counter on Baxter.

Study the Classics

Put a +1/+1 counter on target creature, then double the number of +1/+1 counters on it. You gain life equal to the number of +1/+1 counters on that creature.

Rootbound Crag

This land enters tapped unless you control a Mountain or a Forest.
{T}: Add {R} or {G}.

Treasure

{T}, Sacrifice this token: Add one mana of any color.

Plains

Forest

Rain-Slicked Copse

({T}: Add {G} or {U}.)
This land enters tapped.
Cycling {2} ({2}, Discard this card: Draw a card.)

Dimension X Pizzasaur

When this creature enters, put two +1/+1 counters on target creature. When you do, destroy up to one target creature with mana value less than or equal to the number of counters among permanents you control.
{2}, {T}, Sacrifice this creature: You gain 3 life and each opponent loses 3 life.

Arcane Signet

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

Sunken Hollow

({T}: Add {U} or {B}.)
This land enters tapped unless you control two or more basic lands.

Sodden Verdure

({T}: Add {G} or {U}.)
This land enters tapped unless you control two or more basic lands.

Steelbane Hydra

This creature enters with X +1/+1 counters on it.
{2}{G}, Remove a +1/+1 counter from this creature: Destroy target artifact or enchantment.

Robot

Clue

Fabled Passage

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Then if you control four or more lands, untap that land.

Big Apple, 3 a.m.

This land enters tapped. As it enters, choose a color.
{T}: Add one mana of the chosen color.
{5}, {T}: Create a 1/1 black Rat creature token for each opponent you have.

Lessons from Life

Draw three cards. You may put a land card from your hand onto the battlefield tapped.

Together Forever

When this enchantment enters, support 2. (Put a +1/+1 counter on each of up to two target creatures.)
{1}: Choose target creature with a counter on it. When that creature dies this turn, return that card to its owner's hand.

Pain 101

Until end of turn, target creature gains deathtouch and "When this creature dies, return it to the battlefield tapped under its owner's control."

Smoldering Marsh

({T}: Add {B} or {R}.)
This land enters tapped unless you control two or more basic lands.

On an Adventure

After an Adventure resolves, you can place the exiled card here. You may cast the creature from exile.

Mutational Advantage

Permanents you control with counters on them gain hexproof and indestructible until end of turn. Prevent all damage that would be dealt to those permanents this turn. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Vigor

Trample
If damage would be dealt to another creature you control, prevent that damage. Put a +1/+1 counter on that creature for each 1 damage prevented this way.
When Vigor is put into a graveyard from anywhere, shuffle it into its owner's library.

Evolution Witness

{1}{G}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Whenever one or more +1/+1 counters are put on this creature, return target permanent card from your graveyard to your hand.

Ninja Pizza

Foods you control have "{T}, Sacrifice this artifact: Add one mana of any color."
At the beginning of your second main phase, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")

Shapeshifter

Mutagen

{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.

Vanquish the Horde

This spell costs {1} less to cast for each creature on the battlefield.
Destroy all creatures.

Hardened Scales

If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.

Ouroboroid

At the beginning of combat on your turn, put X +1/+1 counters on each creature you control, where X is this creature's power.

Big Mother Mouser

This creature enters with two +1/+1 counters on it.
Whenever this creature attacks, double the number of +1/+1 counters on it.
When this creature dies, create a number of 1/1 colorless Robot artifact creature tokens equal to the number of +1/+1 counters on this creature.

Heroes in a Half Shell

Vigilance, menace, trample, haste
Whenever one or more Mutants, Ninjas, and/or Turtles you control deal combat damage to a player, put a +1/+1 counter on each of those creatures and draw a card.

Kalonian Hydra

Trample
This creature enters with four +1/+1 counters on it.
Whenever this creature attacks, double the number of +1/+1 counters on each creature you control.

Foot Chopper

When this Equipment enters, create a 1/1 black Ninja creature token, then attach this Equipment to it.
Equipped creature has flying.
Whenever equipped creature deals combat damage to a player, you may sacrifice it. If you do, draw cards equal to its power.
Equip {2}

Corpsejack Menace

If one or more +1/+1 counters would be put on a creature you control, twice that many +1/+1 counters are put on it instead.

Leonardo, the Balance

Whenever a token you control enters, you may put a +1/+1 counter on each creature you control. Do this only once each turn.
{W}{U}{B}{R}{G}: Creatures you control gain menace, trample, and lifelink until end of turn.
Partner—Character select (You can have two commanders if both have this ability.)

Mutagen Man, Living Ooze

Trample
Activated abilities of artifact tokens you control cost {1} less to activate.
When Mutagen Man enters, create X Mutagen tokens. (They're artifacts with "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")

Innkeeper's Talent

(Gain the next level as a sorcery to add its ability.)
At the beginning of combat on your turn, put a +1/+1 counter on target creature you control.
{G}: Level 2
Permanents you control with counters on them have ward {1}.
{3}{G}: Level 3
If you would put one or more counters on a permanent or player, put twice that many of each of those kinds of counters on that permanent or player instead.

Agatha's Soul Cauldron

You may spend mana as though it were mana of any color to activate abilities of creatures you control.
Creatures you control with +1/+1 counters on them have all activated abilities of all creature cards exiled with Agatha's Soul Cauldron.
{T}: Exile target card from a graveyard. When a creature card is exiled this way, put a +1/+1 counter on target creature you control.

Sol Ring

Ninja

High Score

If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.
At the beginning of your end step, draw a card if you control a creature with the greatest power among creatures on the battlefield.

Undergrowth Stadium

This land enters tapped unless you have two or more opponents.
{T}: Add {B} or {G}.

Make Your Move

Destroy target artifact, enchantment, or creature with power 4 or greater.

Island

Cinder Glade

({T}: Add {R} or {G}.)
This land enters tapped unless you control two or more basic lands.

Academy Manufactor

If you would create a Clue, Food, or Treasure token, instead create one of each.

Michelangelo, the Heart

Trample
Raid (the Fridge) — At the beginning of your second main phase, if you attacked this turn, put a +1/+1 counter on target creature and create a Food token.
Partner—Character select (You can have two commanders if both have this ability.)

Roadkill Rodney

Squad {3} (As an additional cost to cast this spell, you may pay {3} any number of times. When this creature enters, create that many tokens that are copies of it.)
Deathtouch
Whenever this creature deals combat damage to a player, create a Mutagen token.

Abundant Countryside

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell.
{6}, {T}: Create a 1/1 colorless Shapeshifter creature token with changeling. (It's every creature type.)

Food

{2}, {T}, Sacrifice this token: You gain 3 life.

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Donatello, the Brains

If one or more tokens would be created under your control, those tokens plus a Mutagen token are created instead.
Partner—Character select (You can have two commanders if both have this ability.)

Assassin's Trophy

Destroy target permanent an opponent controls. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Rocksteady, Mutant Marauder

Partner with Bebop, Skull & Crossbones (When this creature enters, target player may put Bebop into their hand from their library, then shuffle.)
Trample
Whenever another nontoken creature you control enters, put a +1/+1 counter on target creature.

Michelangelo, Weirdness to 11

When Michelangelo enters, create a Mutagen token. (It's an artifact with "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")
If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.

City of Brass

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

Mona Lisa, Science Geek

Reach
{T}: Add X mana of any one color, where X is Mona Lisa's power.

Swamp

Hinterland Harbor

This land enters tapped unless you control a Forest or an Island.
{T}: Add {G} or {U}.

Tempestra, Dame of Games

{2}{R}, {T}, Sacrifice an artifact: Create a token that's a copy of another target creature you control, except it isn't legendary. It gains haste. Sacrifice it at the beginning of the next end step.

Command Tower

Mikey & Leo, Chaos & Order

Whenever you put a counter on a creature you control, draw a card. This ability triggers only once each turn.

Arcade Cabinet

When this artifact enters, put a +1/+1 counter on each of up to four target creatures.
{2}, {T}, Sacrifice a token: Double the number of each kind of counter on target creature.

Ardenvale Fealty

Create a 2/2 white Knight creature token with vigilance. (Then exile this card. You may cast the enchantment later from exile.)

Virtue of Loyalty

At the beginning of your end step, put a +1/+1 counter on each creature you control. Untap those creatures.

Virtue of Loyalty // Ardenvale Fealty

Hidden Hideout

This land enters tapped.
{T}: Add one mana of any color in your commander's color identity.
{2}, {T}: Target creature you control with a counter on it gains lifelink until end of turn.

Thriving Moor

This land enters tapped. As it enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

Exotic Orchard

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

Thriving Grove

This land enters tapped. As it enters, choose a color other than green.
{T}: Add {G} or one mana of the chosen color.

Tainted Treats

Destroy target artifact or creature. If its mana value was 4 or less, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")

Branching Evolution

If one or more +1/+1 counters would be put on a creature you control, twice that many +1/+1 counters are put on that creature instead.

Swift Demise

Swift Demise deals 1 damage to target creature. Then destroy each creature you don't control that was dealt damage this turn.

Leatherhead, Iron Gator

Trample, haste
Whenever Leatherhead attacks, put two +1/+1 counters on each creature you control.

Splinter, the Mentor

Menace
Whenever Splinter or another nontoken creature you control leaves the battlefield, create a Mutagen token.
Partner—Character select (You can have two commanders if both have this ability.)

Path of Ancestry

This land enters tapped.
{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)