Card

Splinter's Technique

Teenage Mutant Ninja Turtles Art Series

Krang & Shredder

Teenage Mutant Ninja Turtles

Legendary Creature — Mutant Ninja Turtle

Sneak {3}{W}{W} (You may cast this spell for {3}{W}{W} if you also return an unblocked attacker you control to hand during the declare blockers step. He enters tapped and attacking.)
When Leonardo enters, if his sneak cost was paid, creatures you control get +2/+0 until end of turn.
{1}{W}: Leonardo gains first strike until end of turn.

Leonardo, Leader in Blue

Flying
Whenever an artifact you control enters, put a +1/+1 counter on Donatello.

Donatello, Way with Machines

Mutagen

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.")

Michelangelo, Mutant BFF

Menace (This creature can't be blocked except by two or more creatures.)
Alliance — Whenever another creature you control enters, you may exile the top card of your library.
Whenever Raphael attacks, until end of turn, you may play a card exiled with Raphael.

Raphael, Most Attitude

Sorcery

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.

Instant

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.

Raphael's Technique

Legendary Creature — Utrom Human Ninja

Whenever Krang & Shredder enter or attack, each opponent exiles cards from the top of their library until they exile a nonland card.
Disappear — At the beginning of your end step, if a permanent left the battlefield under your control this turn, you may cast a card exiled with Krang & Shredder without paying its mana cost.

Secret Lair Drop

Creature — Human Warrior

As this creature enters, choose a creature type.
Whenever a creature of the chosen type dies, you may draw a card.

Species Specialist

Creature — Human Warlock

Rats you control have menace.
{1}{B}, {T}: Create a 1/1 black Rat creature token.
{2}{B}{B}, {T}, Sacrifice three Rats: Gain control of target creature.