What happens to items left in Mordenkainen's Magnificent Mansion?

Question

Recently, the question arose as to what happens when you leave objects you own in Mordenkainen's Magnificent Mansion. The spell description does not specify if you always conjure the same Mansion, or if it is a different one. So what happens if I leave something like my magic short sword in it? Or even a mundane item, like my mundane pottery?

The spell says that creatures are expelled when the spell ends, and it says what happens to things from the mansion that you want to take outside, but there is nothing about items taken into the mansion. Is there any information in the rules, somewhere?

Answer 1

Short answer, they would be expelled too, unless you give the order to preserve it to one of the servant but the item will be lost forever.

Long answer:

Is the same mansion? No.

PHB 261:

You conjure an extradimensional dwelling in range that lasts for the duration.

As you can read it does not say you conjure a new or an existing mansion. Later on in the same description, it state that you can create but it does tell you anything about reusing the existing one. It also does not stop you to recreate an old one, but is not going to be the same one. Furthermore, at any point on the description says something about the servants remembering you, reinforcing the idea that is a totally new one.

You can create any floor plan you like

What happen to the item left?

Following the same logic, the spell description also state what the servant can do, under their limits. And since you can give things to humans, it is safe to assume that you can give to them items. You can order to keep the item, but as stated earlier the item will be lost.

Each servant can perform any task a normal human servant could perform, but they can’t attack or take any action that would directly harm another creature.

Now, what would happen to items that you leave in the mansion? The "mansion" does not hold ownership on any item that you have or leave behind. The same way you do not own any items in the mansion (you cannot take them out). So, unless you "give" to the mansion the ownership of an item, it would behave as if the Object is a Creature and drop it.

The servants can go anywhere in the mansion but can’t leave it. Furnishings and other objects created by this spell dissipate into smoke if removed from the mansion.

When the spell ends, any creatures inside the extradimensional space are expelled into the open spaces nearest to the entrance.

We can expand the ownership logic further. The nourishment of the food given by the spell does not disappear at the end of the spell or when you leave the mansion, but the furniture do. This mean that in order to take things out of the mansion they have to be given. This logic can be applied to your own stuffs. The "mansion" does not have any ownership of your stuff, hence, they are expelled from the mansion when the spell end (given that you did not give them to a servant).

It contains sufficient food to server a nine-course banquet for up to 100 people

Now, you might want to say: a creature is not an object. And it is true, but it is more of a mechanical way to delimit and categorize elements in the game. That would be a total debate but as far as your question goes is not that relevant. Furthermore, your DM is the one that has the last word, if you are the DM pick what would be more sensible for you.

Answer 2

Rules as Written doesn't clearly answer the question. I believe Rules as Intended would not allow any object to remain in the house and would drop them when the spell ends. For, it can safely be assumed that:

When the spell ends, any creatures inside the extradimensional space are expelled into the open spaces nearest to the entrance.

would include their gear and clothes. I doubt the designers intended the mansion to eat all the party's gear and clothes and leave them nude and unarmed.

If their gear and clothes are expelled, why would a sword they left in another room be any different? Moreover, the extradimensional space is described fairly similar to rope trick, which does expel everything left inside.

There is no mention of "giving" to the Mansion or any ownership. If it is created by the spell, it can't leave the Mansion. But objects you leave in it were not created by the spell.

As a DM, I might rule differently depending on what it is the players try to leave behind. If it is an art piece or something funny, I might allow it; but in general leaving a powerful item there to protect it isn't going to fly.

This answer has since been confirmed by the latest Sage Advice update:

What happens to objects brought inside and left inside Mordenkainen’s magnificent mansion when the spell ends?

The intent is that the objects are ejected from the mansion when the spell ends and appear in unoccupied spaces closest to where the door was. This intent will be reflected in future printings of the Player’s Handbook.

Answer 3

You could rule that recasting the mansion at the same spot it was originally cast and before the duration expires always keeps the same mansion active.

The persistence time between castings could be extended at DM’s discretion, though the caster may wish to create a new mansion in order to change the floorplan, repair furnishings, etc. If the recast time elapses or the caster wishes to ‘reset’ the mansion, any non-native items could be expelled like creatures are.

I wouldn’t allow the mansion to be mobile relative to the world it was cast on. Standing by or on a plank when casting wouldn’t allow the mansion’s entrance to be moved by moving the plank. Even so, the mansion’s location isn’t fixed in an independent reference frame, so planetary revolution and rotation wouldn’t mean your mansion’s door is now in outer space. The entrance point is fixed relative to the most significant local gravity well, generally your planet.

Answer 4

Of all the answers, including the currently accepted one, only J. A. Streich has accepted V2Blast's suggestion to update to accommodate the then-new (2020) Sage Advice ruling, which said:

What happens to objects brought inside and left inside Mordenkainen’s magnificent mansion when the spell ends? The intent is that the objects are ejected from the mansion when the spell ends and appear in unoccupied spaces closest to where the door was. This intent will be reflected in future printings of the Player’s Handbook."

Since then we have actually been able to see the new version of the spell, currently available on D&D Beyond, which says (emphasis mine):

When the spell ends, any creatures or objects left inside the extradimensional space are expelled into the open spaces nearest to the entrance.

However, even before this change, it was possible to refute one of the OP's assertions, "The spell description does not specify if you always conjure the same Mansion, or if it is a different one."

While it is true that the spell description does not explicitly address whether a new-cast mansion is the same as one previously cast, the spell does say:

It contains sufficient food to serve a nine-course banquet for up to 100 people.

The PC's may eat this food, reducing the total amount, during the 24 hour duration of the spell. If this was the same mansion on the next cast, it would not then have food for 100 people; it would have lost the food eaten since the last time it was cast. Thus the spell, when cast, would not match the description given. Further, every time the spell was used, it would be of decreased utility, until the caster was summoning a mansion with no food inside, which is both a mechanic unlike any other spell and a strange limitation for a spell of 7th level.

The spell also says:

The place is furnished and decorated as you choose...Furnishings and other objects created by this spell dissipate into smoke if removed from the mansion.

It does not say that furniture removed from the mansion returns to it; rather, such things disappear. If they are no longer present when the spell is cast again, then it does not match the spell description which says the caster may furnish it as they choose. And if the chosen furnishings are present even after 'disappearing', then it is clearly not the same mansion.

Thus from the spell description itself it is strongly implied that you get a new mansion upon each casting, and can thus re-arrange the layout each time. This is in direct contrast to the spell demiplane which explicitly gives the caster the choice to open a portal to a new demiplane or one previously created, and which also explicitly says that any demiplane created persists indefinitely after the casting, even though the door lasts only one hour.

Answer 5

I see a lot of people giving a lot of speculative ideas, but still ignoring the simplicity of what is stated. The spell says creatures are expelled, and that can be interpreted to mean all items on their person. However, to think that this is a completely new mansion each time cast is preposterous, and not within the rules as presented. A DM may rule that to be the case, but it is just as easy to think that the plan may change, but the amount of space reserved for the casting mage to actually be the exact same. Practically speaking, it is meant to be a home that the mage can revisit. It makes sense that you might like to keep certain things you bring in there, like a pile of gold, or old magic items. In my ideal version I have made a vault. You can't bring the servants or the objects native to this space out, but there is nothing in the description that prohibits making rooms for each party member that persist each time the spell is cast. Or you could install an alchemy lab, stocking it with real world agents and vials, so that they could then be taken out of this space. You can have shelves stocked with real books, old spellbooks, etc. Or a trophy room to safely store items gleaned from adventuring. This approach would mean that these spaces are created first by the wizard, linked somewhere on the Astral plane, but that even after his death, these spaces may persist, be discovered and looted somehow, by DM approval of course.

To compare it to weaker spells, like Rope Trick, is not valid, because they are lower level, and therefore less capable. Rope trick creates a nondescript space to simply rest in. The Mansion creates a furnished environment, fully customizeable, even with semi-sentient servants. Something to think about.