Deadly Rollick

If you control a commander, you may cast this spell without paying its mana cost.
Exile target creature.

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.

Dark Leo & Shredder

Sneak {W}{B}
Attacking Ninjas you control have deathtouch.
Whenever Dark Leo & Shredder deal combat damage to a player, create a 1/1 black Ninja creature token. Then if you control five or more Ninjas, that player loses half their life, rounded up.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

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.)

Dark Ritual

Sol Ring

The Last Ronin'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.)
Create three 1/1 white Ninja Turtle Spirit creature tokens. If this spell's sneak cost was paid, they enter tapped and attacking.

Wound Reflection

At the beginning of each end step, each opponent loses life equal to the life they lost this turn. (Damage causes loss of life.)

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Vampiric Tutor

Search your library for a card, then shuffle and put that card on top. You lose 2 life.

Changeling Outcast

Changeling (This card is every creature type.)
This creature can't block and can't be blocked.

Demonic Tutor

Search your library for a card, put that card into your hand, then shuffle.

Grand Abolisher

During your turn, your opponents can't cast spells or activate abilities of artifacts, creatures, or enchantments.

Ninja Teen

(Gain the next level as a sorcery to add its ability.)
Whenever a creature you control leaves the battlefield, each opponent loses 1 life.
{1}{B}: Level 2
Creatures you control get +1/+0 and have menace.
{B}: Level 3
Creature cards in your graveyard have sneak {3}{B}.
You may cast creature spells from your graveyard using their sneak abilities.

Flawless Maneuver

If you control a commander, you may cast this spell without paying its mana cost.
Creatures you control gain indestructible until end of turn.

Roaming Throne

Ward {2}
As this creature enters, choose a creature type.
This creature is the chosen type in addition to its other types.
If a triggered ability of another creature you control of the chosen type triggers, it triggers an additional time.

Throatseeker

Unblocked attacking Ninjas you control have lifelink.

Deadly Dispute

As an additional cost to cast this spell, sacrifice an artifact or creature.
Draw two cards and create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")