Genghis Frog

Trample
Whenever Genghis Frog or another Mutant you control 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.")

Jason Bright, Glowing Prophet

Whenever a Zombie or Mutant you control dies, if its power was different from its base power, draw a card.
Come Fly With Me — {2}, Sacrifice a creature: Put a +1/+1 counter on target creature you control. It gains flying until end of turn.

Rejuvenating Springs

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

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.)

Lessons from Life

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

Herald's Horn

As this artifact enters, choose a creature type.
Creature spells you cast of the chosen type cost {1} less to cast.
At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.

Omni-Changeling

Changeling (This card is every creature type.)
Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
You may have this creature enter as a copy of any creature on the battlefield, except it has changeling.

Willowrush Verge

{T}: Add {U}.
{T}: Add {G}. Activate only if you control a Forest or an Island.

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.

Vineglimmer Snarl

As this land enters, you may reveal a Forest or Island card from your hand. If you don't, this land enters tapped.
{T}: Add {G} or {U}.

Yavimaya Coast

{T}: Add {C}.
{T}: Add {G} or {U}. This land deals 1 damage to you.

Wave Goodbye

Return each creature without a +1/+1 counter on it to its owner's hand.

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.)

Elvish Mystic

Pongify

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

Arcane Signet

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

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Loading Zone

If one or more counters would be put on a creature, Spacecraft, or Planet you control, twice that many of each of those kinds of counters are put on it instead.
Warp {G} (You may cast this card from your hand for its warp cost. Exile this enchantment at the beginning of the next end step, then you may cast it from exile on a later turn.)

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.

Llanowar Elves

Ozolith, the Shattered Spire

If one or more +1/+1 counters would be put on an artifact or creature you control, that many plus one +1/+1 counters are put on it instead.
{1}{G}, {T}: Put a +1/+1 counter on target artifact or creature you control. Activate only as a sorcery.
Cycling {2} ({2}, Discard this card: Draw a card.)

Birds of Paradise

Leatherhead, Swamp Stalker

Trample
Leatherhead enters with a hexproof counter on her.
Whenever Leatherhead deals combat damage to a player, you may remove a counter from her. When you do, destroy target artifact or enchantment that player controls.

Crustacean Commando

When this creature 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.")

Misty Rainforest

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

Kami of Whispered Hopes

If one or more +1/+1 counters would be put on a permanent you control, that many plus one +1/+1 counters are put on that permanent instead.
{T}: Add X mana of any one color, where X is this creature's power.

Island

Command Tower

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.")

Benthic Biomancer

{1}{U}: Adapt 1. (If this creature has no +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever one or more +1/+1 counters are put on this creature, draw a card, then discard a card.

Experimental Augury

Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order. Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Forest

Master Biomancer

Each other creature you control enters with a number of additional +1/+1 counters on it equal to this creature's power and as a Mutant in addition to its other types.

Bristly Bill, Spine Sower

Landfall — Whenever a land you control enters, put a +1/+1 counter on target creature.
{3}{G}{G}: Double the number of +1/+1 counters on each creature you control.

Simic Ascendancy

{1}{G}{U}: Put a +1/+1 counter on target creature you control.
Whenever one or more +1/+1 counters are put on a creature you control, put that many growth counters on this enchantment.
At the beginning of your upkeep, if this enchantment has twenty or more growth counters on it, you win the game.

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.

Lumbering Megasloth

This spell costs {1} less to cast for each counter among players and permanents.
Trample
This creature enters tapped.

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

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.

Mutant Chain Reaction

Destroy up to one target artifact, enchantment, or creature with flying. 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.")

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.")

Marwyn, the Nurturer

Whenever another Elf you control enters, put a +1/+1 counter on Marwyn.
{T}: Add an amount of {G} equal to Marwyn's power.

Waterlogged Grove

{T}, Pay 1 life: Add {G} or {U}.
{1}, {T}, Sacrifice this land: Draw a card.

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

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."

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.

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Formless Genesis

Changeling (This card is every creature type.)
Create an X/X colorless Shapeshifter creature token with changeling and deathtouch, where X is the number of land cards in your graveyard.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Growth Spiral

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

Negate

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.

Gyre Sage

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
{T}: Add {G} for each +1/+1 counter on this creature.

Breeding Pool

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

Preordain

Scry 2, then draw a card. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

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.)

Mona Lisa, Science Geek

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

The Earth Crystal

Green spells you cast cost {1} less to cast.
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.
{4}{G}{G}, {T}: Distribute two +1/+1 counters among one or two target creatures you control.

Guardian Gladewalker

Changeling (This card is every creature type.)
When this creature enters, put a +1/+1 counter on target creature.

Counterspell

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.

The Ozolith

Whenever a creature you control leaves the battlefield, if it had counters on it, put those counters on The Ozolith.
At the beginning of combat on your turn, if The Ozolith has counters on it, you may move all counters from The Ozolith onto target creature.

Swan Song

Counter target enchantment, instant, or sorcery spell. Its controller creates a 2/2 blue Bird creature token with flying.

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.)

Mutable Explorer

Changeling (This card is every creature type.)
When this creature enters, create a tapped Mutavault token. (It's a land with "{T}: Add {C}" and "{1}: This token becomes a 2/2 creature with all creature types until end of turn. It's still a land.")

Mona Lisa, Ever Adaptable

Whenever a player casts a creature spell, you 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.")

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.

Pollywog Prodigy

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Whenever an opponent casts a noncreature spell with mana value less than this creature's power, draw a card.

Heroic Intervention

Permanents you control gain hexproof and indestructible until end of turn.

Sol Ring

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Plaxcaster Frogling

Graft 3 (This creature enters with three +1/+1 counters on it. Whenever another creature enters, you may move a +1/+1 counter from this creature onto it.)
{2}: Target creature with a +1/+1 counter on it gains shroud until end of turn. (It can't be the target of spells or abilities.)

An Offer You Can't Refuse

Counter target noncreature spell. Its controller creates two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Thrummingbird

Flying
Whenever this creature 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.)