Splinter's Technique

Sneak {1}{B} (You may cast this spell for {1}{B} if you also return an unblocked attacker you control to hand during the declare blockers step.)
Search your library for a card, put that card into your hand, then shuffle.

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.)

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.

Leonardo, Cutting Edge

Sneak {W} (You may cast this spell for {W} if you also return an unblocked attacker you control to hand during the declare blockers step. He enters tapped and attacking.)
Lifelink
Whenever you gain life, put a +1/+1 counter on Leonardo.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice this artifact: Draw a card.

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.)

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.

Raphael's Technique

Sneak {2}{R} (You may cast this spell for {2}{R} if you also return an unblocked attacker you control to hand during the declare blockers step.)
Each player may discard their hand and draw seven cards.

Turtles in Time

Return all creatures to their owners' hands. Each player may shuffle their hand and graveyard into their library, then each player who does draws seven cards.
Exile Turtles in Time.

Super Shredder

Menace
Whenever another permanent leaves the battlefield, put a +1/+1 counter on Super Shredder.

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Michelangelo, Improviser

Sneak {2}{G}{G} (You may cast this spell for {2}{G}{G} if you also return an unblocked attacker you control to hand during the declare blockers step. He enters tapped and attacking.)
Whenever Michelangelo deals combat damage to a player, you may put a creature card and/or a land card from your hand onto the battlefield.

Cool but Rude

(Gain the next level as a sorcery to add its ability.)
Whenever you attack, you may discard a card. If you do, draw a card.
{1}{R}: Level 2
Whenever you discard a card, this Class deals 2 damage to each opponent.
{1}{R}: Level 3
When this Class becomes level 3, search your library for a card, put it into your hand, shuffle, then discard a card at random.

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.

Leonardo, Worldly Warrior

This spell costs {1} less to cast for each creature you control.
Double strike (This creature deals both first-strike and regular combat damage.)

Raph & Mikey, Troublemakers

Trample, haste
Whenever Raph & Mikey attack, reveal cards from the top of your library until you reveal a creature card. Put that card onto the battlefield tapped and attacking and the rest on the bottom of your library in a random order.

Prismatic Omen

Lands you control are every basic land type in addition to their other types.

Doubling Season

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.
If an effect would put one or more counters on a permanent you control, it puts twice that many of those counters on that permanent instead.

Splinter, Radical Rat

If an ability of a Ninja creature you control triggers, that ability triggers an additional time.
{1}{U}: Target Ninja can't be blocked this turn.

Mirrorworks

Whenever another nontoken artifact you control enters, you may pay {2}. If you do, create a token that's a copy of that artifact.

Teferi's Protection

Until your next turn, your life total can't change and you gain protection from everything. All permanents you control phase out. (While they're phased out, they're treated as though they don't exist. They phase in before you untap during your untap step.)
Exile Teferi's Protection.

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.)

Command Tower

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

Armaggon, Future Shark

Flash
When Armaggon enters, destroy up to three target creatures.

Turtle Power!

Donatello, Gadget Master

Sneak {1}{U} (You may cast this spell for {1}{U} if you also return an unblocked attacker you control to hand during the declare blockers step. He enters tapped and attacking.)
Whenever Donatello deals combat damage to a player, create a token that's a copy of target artifact you control.

Slash, Reptile Rampager

Alliance — Whenever another creature you control enters, Slash deals 2 damage to each opponent.
Whenever Slash attacks, create a 2/2 red Mutant creature token.

Swamp

Rhythm of the Wild

Creature spells you control can't be countered.
Nontoken creatures you control have riot. (They enter with your choice of a +1/+1 counter or haste.)

Forest

Sol Ring

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.

The Last Ronin

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Destroy all creatures.
II — Mill four cards. When you do, return target creature card from your graveyard to your hand.
III — Whenever a creature you control attacks alone this turn, put three +1/+1 counters on it. It gains trample, lifelink, and indestructible until end of turn.

Mirage Mirror

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

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.)

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.)

Donatello, Rad Scientist

Vigilance (Attacking doesn't cause this creature to tap.)
When Donatello enters, tap up to three target creatures your opponents control. Put a stun counter on each of them. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Island

Leonardo, Sewer Samurai

Sneak {2}{W}{W}
Double strike
During your turn, you may cast creature spells with power or toughness 1 or less from your graveyard. If you cast a spell this way, that creature enters with a finality counter on it. (If a creature with a finality counter on it would die, exile it instead.)

Heroic Intervention

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

Tokka & Rahzar, Terrible Twos

This spell can't be countered.
Menace
Whenever a player casts a spell, if the amount of mana spent to cast it was less than its mana value, Tokka & Rahzar deal 3 damage to that player.

Groundchuck & Dirtbag

Trample
Whenever you tap a land for mana, add {G}.

Raphael, Tag Team Tough

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Raphael deals combat damage to a player for the first time each turn, untap all attacking creatures. After this combat phase, there is an additional combat phase.

Michelangelo, On the Scene

Trample (This creature can deal excess combat damage to the player it's attacking.)
Michelangelo enters with a +1/+1 counter on him for each land you control.
When Michelangelo dies, return this card to your hand.

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.

Reliquary Tower

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

Raphael, the Nightwatcher

Sneak {1}{R}{R} (You may cast this spell for {1}{R}{R} if you also return an unblocked attacker you control to hand during the declare blockers step. He enters tapped and attacking.)
Attacking creatures you control have double strike.

Urza's Incubator

As this artifact enters, choose a creature type.
Creature spells of the chosen type cost {2} less to cast.

Don & Leo, Problem Solvers

Vigilance
At the beginning of your end step, exile up to one target artifact you control and up to one target creature you control. Then return them to the battlefield under their owners' control.

Plains

Mountain

Aggravated Assault

{3}{R}{R}: Untap all creatures you control. After this main phase, there is an additional combat phase followed by an additional main phase. Activate only as a sorcery.

Turtles Forever

Search your library and/or outside the game for exactly four legendary creature cards you own with different names, then reveal those cards. An opponent chooses two of them. Put the chosen cards into your hand and shuffle the rest into your library.

Ashnod's Altar

Propaganda

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Dark Ritual

Seedborn Muse

Untap all permanents you control during each other player's untap step.

Battle Hymn

Omniscience

You may cast spells from your hand without paying their mana costs.

Broadcast Takeover

Gain control of all artifacts your opponents control until end of turn. Untap them. They gain haste until end of turn.

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.")

Michelangelo's Technique

Sneak {3}{G} (You may cast this spell for {3}{G} if you also return an unblocked attacker you control to hand during the declare blockers step.)
Look at the top eight cards of your library. Put up to two creature cards with total mana value 6 or less from among them onto the battlefield and the rest on the bottom of your library in a random order.

Raph & Leo, Sibling Rivals

Whenever Raph & Leo attack, if it's the first combat phase of the turn, untap one or two target attacking creatures. After this phase, there is an additional combat phase.

Chromatic Lantern

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

Leonardo's Technique

Sneak {1}{W} (You may cast this spell for {1}{W} if you also return an unblocked attacker you control to hand during the declare blockers step.)
Return one or two target creature cards each with mana value 3 or less from your graveyard to the battlefield.

Mikey & Leo, Chaos & Order

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

The Great Henge

This spell costs {X} less to cast, where X is the greatest power among creatures you control.
{T}: Add {G}{G}. You gain 2 life.
Whenever a nontoken creature you control enters, put a +1/+1 counter on it and draw a card.

Mikey & Don, Party Planners

Ward {2}
You may look at the top card of your library any time.
You may play lands and cast Mutant, Ninja, or Turtle spells from the top of your library. If you cast a creature spell this way, that creature enters with an additional +1/+1 counter on it.