Splinter, the Mentor — ruling 1

An effect that checks whether you control your commander is satisfied if you control one or both of your two commanders.

Splinter, the Mentor — ruling 2

Some spells and abilities that create Mutagen tokens require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve. The Mutagen token won't be created.

Splinter, the Mentor — ruling 3

Mutagen tokens are a kind of predefined token. Each one is a colorless artifact with the artifact subtype Mutagen and the ability "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery."

Splinter, the Mentor — ruling 4

To have two commanders, both must have appropriate partner abilities as the game begins. Losing the ability during the game doesn't cause either to cease to be your commander.

Splinter, the Mentor — ruling 5

You can have two commanders if each one has "Partner—Character select." You can't mix and match them with cards that have other partner abilities.

Splinter, the Mentor — ruling 6

If your Commander deck has two commanders, you can only include cards whose own color identities are also found in your commanders' combined color identities. If Donatello, the Brains and Splinter, the Mentor are your commanders, your deck may contain cards with blue and/or black in their color identity, but not cards with red, green, or white. (If Leonardo, the Balance is one of your commanders, your deck may contain cards with any color or combination of colors in their color identity, regardless of who your other commander is.)

Splinter, the Mentor — ruling 7

Both commanders start in the command zone, and the remaining 98 cards of your deck are shuffled to become your library.

Splinter, the Mentor — ruling 8

Once the game begins, your two commanders are tracked separately. If you cast one, you won't have to pay an additional {2} the first time you cast the other. A player loses the game after having been dealt 21 damage from any one of them, not from both of them combined.

Splinter, the Mentor : règles, fonctionnement et interactions (MTG)

Splinter, the Mentor is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

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.)

Complete guide

Splinter, the Mentor is a versatile legendary creature that rewards you for the movement of your units between zones. As a master of mutation, he ensures that even when your creatures fall or retreat, they leave behind the tools for your remaining forces to grow stronger.

The Master of Mutagens

Splinter, the Mentor features a triggered ability that triggers whenever he or another nontoken creature you control leaves the battlefield. This covers a wide range of actions: dying, being exiled, being returned to your hand, or even being put into your library. When this happens, you create a Mutagen token. These tokens are predefined colorless artifacts that can be sacrificed for one mana at sorcery speed to place a +1/+1 counter on a target creature.

Step-by-Step Resolution

First, a nontoken creature you control must move from the battlefield to any other zone. This immediately triggers Splinter's ability. The trigger is put onto the stack and, when it resolves, you create a Mutagen token. Once the token is on the battlefield, you can activate its ability by paying {1}, tapping it, and sacrificing it. You must choose a legal target for the +1/+1 counter. If the target becomes illegal before the ability resolves, the ability fails and no counter is placed.

Character Selection and Commands

Splinter features the 'Partner—Character select' ability, allowing you to have two commanders if both possess this specific keyword. While they share the command zone, they are tracked individually for the 'commander tax' and for commander damage. If an effect refers to 'your commander' while you have two, you choose which one the effect applies to at that moment.

Tactical Timing

Because Mutagen tokens can only be activated as a sorcery, you cannot use them to buff your creatures during combat or in response to a removal spell. You should plan your turn ahead, using your second main phase to buff survivors of combat or your first main phase to prepare for an aggressive swing.

Interaction examples

Generating Value from Sacrifice

Splinter, the Mentor

Blood Artist

If you control both Splinter, the Mentor and Blood Artist and the Blood Artist dies, two triggers occur. Blood Artist triggers to drain 1 life from an opponent, and Splinter triggers because a nontoken creature left the battlefield. You will gain 1 life, your opponent loses 1 life, and you create a Mutagen token.

Mana and Mutation

Splinter, the Mentor

Ornithopter of Paradise

If your Ornithopter of Paradise is destroyed by an opponent's spell, Splinter, the Mentor sees this nontoken creature leave the battlefield. You create a Mutagen token. On your next turn, you can spend {1} and sacrifice that Mutagen to put a +1/+1 counter on Splinter, the Mentor, making him a 3/5 with Menace.

A Master's Exit

Splinter, the Mentor

If an opponent casts a spell to return Splinter, the Mentor to your hand, his own ability triggers because he is a nontoken creature leaving the battlefield. Before he returns to your hand, the trigger goes on the stack, and you will receive a Mutagen token even though Splinter is no longer on the board.

Guide written with AI from the official text and rulings. Official English text prevails.

How it works : Splinter, the Mentor

Original English text — Wizards of the Coast / Scryfall

#1January 27, 2026· Wizards of the Coast
An effect that checks whether you control your commander is satisfied if you control one or both of your two commanders.
No other card is named in this ruling.
#2January 27, 2026· Wizards of the Coast
Some spells and abilities that create Mutagen tokens require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve. The Mutagen token won't be created.
Card named in this ruling
Mutagen
#3January 27, 2026· Wizards of the Coast
Mutagen tokens are a kind of predefined token. Each one is a colorless artifact with the artifact subtype Mutagen and the ability ", , Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery."
Card named in this ruling
Mutagen
#4January 27, 2026· Wizards of the Coast
To have two commanders, both must have appropriate partner abilities as the game begins. Losing the ability during the game doesn't cause either to cease to be your commander.
No other card is named in this ruling.
#5January 27, 2026· Wizards of the Coast
You can have two commanders if each one has "Partner—Character select." You can't mix and match them with cards that have other partner abilities.
No other card is named in this ruling.
#6January 27, 2026· Wizards of the Coast
If your Commander deck has two commanders, you can only include cards whose own color identities are also found in your commanders' combined color identities. If Donatello, the Brains and Splinter, the Mentor are your commanders, your deck may contain cards with blue and/or black in their color identity, but not cards with red, green, or white. (If Leonardo, the Balance is one of your commanders, your deck may contain cards with any color or combination of colors in their color identity, regardless of who your other commander is.)
No other card is named in this ruling.
#7January 27, 2026· Wizards of the Coast
Both commanders start in the command zone, and the remaining 98 cards of your deck are shuffled to become your library.
No other card is named in this ruling.
#8January 27, 2026· Wizards of the Coast
Once the game begins, your two commanders are tracked separately. If you cast one, you won't have to pay an additional the first time you cast the other. A player loses the game after having been dealt 21 damage from any one of them, not from both of them combined.
No other card is named in this ruling.
#9January 27, 2026· Wizards of the Coast
If something refers to your commander while you have two commanders, it refers to one of them of your choice. If you are instructed to perform an action on your commander (e.g. put it from the command zone into your hand due to Command Beacon), you choose one of your commanders at the time the effect happens.
No other card is named in this ruling.