The 14th-level School of Illusion wizard feature, Illusory Reality, can make an object in an illusion spell real for one minute (PHB, p. 118):
When you cast an illusion spell of 1st level or higher, you can choose one inanimate, nonmagical object that is part of the illusion and make that object real. You can do this on your turn as a bonus action while the spell is ongoing. The object remains real for 1 minute. For example, you can create an illusion of a bridge over a chasm and then make it real long enough for your allies to cross.
The object can’t deal damage or otherwise directly harm anyone.
If the illusion spell ends before that minute is up, either through the spell's duration finishing, the spell being Dispelled, or the caster losing concentration, does the "real" object persist for the full minute?
Best Answer
The specific Illusory Reality duration beats the general spell duration.
The overarching rule in D&D 5e is that specific beats general:
So while in general an illusion created by a spell lasts exactly as long as the spell lasts, the Illusory Reality class feature has a specific statement about the duration of its effects.
This means that if an illusionist casts a major image of a blacksmith's forge, with a duration of 10 minutes, they can use Illusory Reality to make the anvil from the forge real. If they do this up to nine minutes after casting the major image, after one minute the anvil will stop being real and revert to being an illusion for the remainder of the spell's duration.
If the illusionist uses Illusory Reality immediately before major image ends (because of its duration, or because the illusionist willingly or unwillingly dropped concentration on the spell), the anvil will remain real while the rest of the illusion fades away. After the one minute of reality afforded to the anvil by Illusory Reality, it will neither real nor illusory, and thus cease to exist.