What counts as "one object" for the Illusion wizard's Illusory Reality and Malleable Illusions features?

Question

I DM for a player who is considering creating a School of Illusion Wizard. They have correctly noted that many things about illusions in the game are open to interpretation, and have asked me to let me know how I would rule on several interactions, in the interest of managing their own expectations. The following question asks about one of these interactions, with the intent of finding out if there is a definitive answer, and gathering information about what would be a reasonable/practical ruling that others have made at their tables if there isn't.

The 14th-level School of Illusion wizard feature, Illusory Reality, can make one 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.

Although the intent is that you can only use this feature on one object per illusion spell, this answer suggests you can use it multiple times on the same object while the spell persists.

But what exactly does "one object" mean, in the context of the 6th-level School of Illusion wizard feature, Malleable Illusions (PHB, p.118)?

Starting at 6th level, when you cast an illusion spell that has a duration of 1 minute or longer, you can use your action to change the nature of that illusion (using the spell's normal parameters for the illusion), provided that you can see the illusion.

With Malleable Illusions, you can change an object in an illusion into another object, into a creature, or into something else (like graffiti on a wall).

This answer suggests that if you did so to an object made real with Illusory Reality, the changed object would remain real.

So: it seems like you might be able to make your "one object" real multiple times, while using Malleable Illusions to change it to a different object each time (if you can't alter objects made real with Illusory Reality using Malleable Illusions, just wait until they are illusions again before using MI).

Is this actually possible?

(Obviously you would still only ever be able to have one real object per illusion spell at any particular time.)

As an example, consider this sequence of events:

1. Create an illusory sword (with a spell such as Major Image)
2. Make the sword real with Illusory Reality
3. Wait a minute for the sword to become illusory again (whether you can apply Malleable Illusions to an object made real by Illusory Reality, and thus skip this step, is the subject of this question)
4. Alter the nature of the illusory sword to be an illusory lump of coal instead
5. Try to apply Illusory Reality to make the coal real. Can this be done?

Answer 1

The rules are unclear so it is a DM decision

Let's go through the steps that you lay out:

1. You now have an illusory sword.
2. You now have a real sword.

3. You have an illusory sword.

   So if you let the effects of Illusory Reality wear off by waiting a minute (assuming you still have the same illusion going) that formerly-real object ceases to be real.

   However, nowhere in the rules or spell description does it outline what actually happens to it. It seems very safe to say that the sword goes back to being an illusion after Illusory Reality wears off since nowhere does it say anything about canceling the effect of the illusion spell that created the object.

4. You now have a lump of coal.

5. There are no rules for this. This is where the DM must make a decision.

   As with most things about illusions, the rules are unclear. The DM must make a decision as to whether the illusory sword is the same object as it was before or something new.

   I can easily see both sides of the argument here so it will really come down to how the DM want to play illusions at their table. On one hand, it is still an illusion and (insofar as it is made of anything) is still essentially the made of the same stuff as the sword was. But, Malleable Illusion also simply allows you to change the entire illusion which can mean drastically changing the object or even turning it into multiple objects. If that was the case, a player could potentially argue that the entire illusion was one object regardless of what it is making. I'm sure there are more arguments to be had for either, but the point is that the DM is the only one who can decide it. The rules won't help.

   If the DM says it is the same object in step 4 then this works. You now have coal. Merry Christmas ;).

Answer 2

RAW, you make an object real once per illusion spell

It depends on the DM's adjudication of the Illusory Reality requirements, but rules as written you can make an object real only when you cast a spell:

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.

This can be read as "you apply Illusory Reality when you cast a spell, expending your bonus action in the process". Basically that means "once per illusion spell", not just "once per object". It is a simple, easy to remember principle, the provided PHB example supports it as well. So no, you cannot "apply Illusory Reality" again at step 5, because RAW you can do it only "when you cast an illusion spell".

However, as a DM you can read this as "you apply Illusory Reality when you cast a spell, OR at any time while the spell is ongoing". In this case, you extend the scope of the feature — when the feature can be applied — but there is nothing wrong in interpreting rules in players' favor. It will be your decision, as a DM, and it slightly contradict the rules, but "the rules serve you, not vice versa" (DMG, page 235). If it might be game-breaking in some specific situations is another question.

While not canon any more, JC backs this up - One real object per spell cast (thank you @JohnP):

Illusory Reality is intended to make one illusory object real per illusion spell