The triggered ability of the “partner with itself” keyword still triggers in a Commander game. If your other commander has somehow ended up in your library, you can find it. You can also target another player, whether or not they have that card in their library.
Playtest cards aren’t legal for play in any tournament format other than Mystery Booster Limited formats. On the other hand, we expect they will spice up a wide variety of non-tournament games (as long as everyone’s on the same page about using them!).
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 one of them, not from both of them combined. Command Beacon’s effect puts one into your hand from the command zone, not both.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Marika Lord
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
For many playtest cards, you’ll need to make a generous assumption that basic game rules would be updated to allow them to work. The Mystery Booster 2 Playtest Card Notes section (reproduced here in individual Gatherer rulings) provides guidance for fitting these cards into the existing rules structure.
Playtest cards use a modified version of game symbols, such as {T} and {W}. These modified symbols should be treated as the standard symbols during play.
The second and third abilities represented by Mothers Yamazaki’s “partner with itself” keyword modify the rules for deck construction in the Commander variant and have no function outside of that variant. They are “A Commander deck can have two cards named Mothers Yamazaki” and “You can designate two cards named Mothers Yamazaki as your commanders.”
Both commanders start in the command zone, and the remaining 98 cards (or 58 cards in a Commander Draft game) of your deck are shuffled to become your library.
Mothers Yamazaki’s “partner with itself” represents three abilities. The first is a triggered ability: “When this permanent enters, target player may search their library for a card named Mothers Yamazaki, reveal it, put it into their hand, then shuffle.”
An effect that checks whether you control your commander is satisfied if you control one or both of your two commanders.
