VerifiedFeb 26, 2026
Mirrorform + Y'shtola, Night's Blessed
Overview
When you cast Mirrorform while Y'shtola, Night's Blessed is (or was) on the battlefield, Y'shtola's "Whenever you cast a noncreature spell with mana value 3 or greater" ability will trigger on the cast. When Mirrorform resolves, it makes each nonland permanent you control become a copy of the chosen non-Aura permanent (for example Y'shtola). Because the effect makes permanents into copies rather than causing them to enter the battlefield as new objects, it does not trigger enters- or leaves-the-battlefield abilities . If that copying produces multiple legendary permanents with the same name under the same player's control, the legend rule requires that player to keep one and put the rest into their owners' graveyards . If any of your permanents that were Auras become non-Auras as a result, they cease to be Auras (and 704.5n's rule about illegal Auras doesn't apply to them as Auras anymore) .
Step 1
You cast Mirrorform. That casting is a noncreature spell with mana value 6 (Mirrorform's mana cost is 
), so Y'shtola's "Whenever you cast a noncreature spell with mana value 3 or greater" ability triggers as you cast Mirrorform.
), so Y'shtola's "Whenever you cast a noncreature spell with mana value 3 or greater" ability triggers as you cast Mirrorform.Step 2
Mirrorform resolves. Its effect makes each nonland permanent you control become a copy of the targeted non-Aura permanent (for example, Y'shtola). Because these permanents are changed into copies rather than entering the battlefield as new objects, this copying does not trigger enters-or-leaves-the-battlefield abilities .
Step 3
As a result, many of your permanents (including the original targeted permanent, which becomes a copy of itself) may now have the same name and be legendary if the copied card is legendary.
Step 4
If you end up controlling two or more legendary permanents that share the same name, you must choose one to keep and put the rest into their owners' graveyards under the legend rule .
Step 5
If any of the permanents you controlled were Auras and they became copies of a non-Aura, they cease to be Auras. The rule that sends an Aura to the graveyard when it is attached illegally or not attached applies only while the object is an Aura, so those permanents, now not Auras, are not put into the graveyard for being unattached by that rule .
Step 6
Meanwhile, the triggered ability from casting Mirrorform (that triggered when you cast it) is on the stack and will resolve independently; its resolution dealing damage and gaining life is unaffected by the later copying/changing of permanents.
Resolution
Casting Mirrorform will cause Y'shtola's cast-trigger to trigger on the casting of Mirrorform. When Mirrorform resolves and makes each nonland permanent you control a copy of the targeted non-Aura permanent, those permanents become copies (copying does not cause enters-the-battlefield or leaves-the-battlefield abilities to trigger) . If that results in you controlling two or more legendary permanents with the same name, you must choose one to keep and put the rest into their owners' graveyards per the legend rule . Auras that become copies of a non-Aura will stop being Auras and will not be put into a graveyard under the "illegal Aura" rule simply because they ceased to be Auras; 704.5n only applies to objects that are Auras and are attached illegally or unattached .
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