Can I get trapped in my own Demiplane?

I’ve been looking at the 8th-level spell Demiplane:

When the spell ends, the door disappears, and any creatures or objects inside the demiplane remain trapped there, as the door also disappears from the other side. Each time you cast this spell, you can create a new demiplane, or have the shadowy door connect to a demiplane you created with a previous casting of this spell.

This looks very useful as a portable shelter, or as a vault or prison for items or creatures the party needs to contain. I just have one question about the exact mechanics of the doorway.

If someone is inside the demiplane when the door closes, it explicitly says that they’re stuck there. (It doesn’t say that they can’t use teleport or plane shift, but that’s a separate question.) What it doesn’t say is whether I get stuck. Can you open the door back to your home plane if you’re inside?

Where on the plane does a creature ejected from demiplane go?

The spell Create Demiplane states that "As a standard action, you may eject a creature from your demiplane. […] An ejected creature goes to the closest plane to your demiplane (usually the Astral Plane or the Ethereal Plane, but if you cast this spell on the Material Plane, the creature is sent to the Material Plane)"

The spell however does not specify where on the plane. I personally see 3 options:

  • The creature gets ejected to the place where the "Create Demiplane" spell was cast, this would be supported by the fact that the plane of ejection is tied to the plane of creation
  • The creature gets ejected to the place where it was before entering into the demiplane, this however would go against the rules if the demiplane was created on the Material but the creature came from somewhere else
  • The creature gets ejected to a random place in the destination plane, but in my opinion this option would have been openly specified, possibly with a "mishap" table

Has there been any clarification on this or is there some rule I missed to clear this out?

How does someone (safely) construct, expand & renovate any given demiplane? [closed]

Casting Demiplane allows the caster (warlock or wizard… or sorcerer using Wish… &/or sneaky bard) to have:

  • A Medium-only door (‘Must be this size or smaller to ride – NO OGRES ALLOWED’) that vanishes when spell ends / after one hour.

  • Creates a permanent (30′ x 30′) room of stone &/or wood walls.

This spell has amazing uses yet serious limits which others have questioned:

Question: “How much one can customize the interior of this spell?”

Answer: “If / as / so much as the DM says / so!”


Question: “What the nature of this demiplane for location & tracking purposes?”

Answer: “They must describe it a bit &/or use a ‘tuning fork‘!”

Information on Demiplane is amazingly light, especially for a game system that prides itself on doing the absolute minimum possible for a spell’s casting. This spell is neither useful for combat mechanics nor very clear for role-play purposes.

My concerns with this spell description & use:

  • Does this shadowy connection door between Demiplanes vanish within the hour? The spell description does not specify, so this may be a way to build up a massive interconnected demi-mansion. Can this door stay ‘open’? Can it be a ‘window’ instead? Can the connection between planes let larger creatures through if you double it up multiple shadow doors in one spot?

  • What happens if one adds plane-space expanding magic to this Demiplane? Say you cast a Mordenkainen’s Magnificent Mansion in there – does the whole plane become a bit bigger? Or does this simply not fit? Or does this spell trigger a collapse-explosion similar to sticking a Bag of Holding into a Portable Hole? Can one change the time-passage of the original Demiplane so as to make these space-holder-builder spells permanent?

  • The 5e spell specifies the new parts must be cast OUTSIDE of the original. Is there ANY way to add or expand to the space-size of this 30′ x 30′ plane? Possibly the repeated use of the (non-exhausting) Wish spell? ‘You need not meet any of the requirements’… does that allow one to add bonus space to this walk in closet? Or even make this silly vanishing smoke-door a bit more durable.. or big enough to fit a donkey through?

Base question: Demiplane feels small / simple / specific / stuck. How does an Arch-mage add bits / expand / give it more space for activities?

Answers may include: any of the guides (Volo’s Mordenkainen’s, etc.), tweets from Lord Crawford, Sage Advice, any 5e Unearthed Arcana… or whatever one can find that is RAW, quasi-legal or even slightly more tested than outright home-brew.

Can a gargantuan creature be shoved into a demiplane using polymorph and released into a different plane of existence

For context, my party is going to face a gargantuan (20 by 20 ft. or larger) creature with obscene levels of health, so would it be possible to make a demiplane and polymorph the gargantuan creature down to size and then shove it into the demiplane, trapping it there.

This spell transforms a creature that you can see within range into a new form. An unwilling creature must make a Wisdom saving throw to avoid the effect. The spell has no effect on a shapechanger or a creature with 0 hit points. The transformation lasts for the duration, or until the target drops to 0 hit points or dies. The new form can be any beast whose challenge rating is equal to or less than the target’s (or the target’s level, if it doesn’t have a challenge rating).

After trapping it there, would it be possible to release it in, let’s say, Hell or just a ‘void’? This is saying that the creature has utilised everything it can to resist magic and it is shoved into the demiplane.

This is saying that the creature has utilised everything it can to resist magic and it is shoved into the demiplane.

To what level of detail must you know the contents of a demiplane to connect to it?

The Demiplane spell states (emphasis mine):

Each time you cast this spell, you can create a new demiplane, or have the shadowy door connect to a demiplane you created with a previous casting of this spell. Additionally, if you know the Nature and contents of a demiplane created by a casting of this spell by another creature, you can have the shadowy door connect to its demiplane instead.

How exact must your knowledge of the contents of a demiplane be before you can use this clause in the spell to connect to it?

Some examples of scenarios where you may or may not know enough detail:

  • You know the demiplane solely contains a particular creature, but you don’t know everything that’s in that creature’s pockets.
  • You know the demiplane solely contains a giant pile of gold coins, and roughly how large it is, but don’t know exactly how many coins there are.
  • The demiplane contains 20 distinct items, and you know 19 of them.

What would happen to a demiplane created by the Demiplane spell if you cast Earthquake inside it?

The demiplane spell creates a door (and a demiplane) that leads to an extradimensional room of a fixed size:

[…] When opened, the door leads to a demiplane that appears to be an empty room 30 feet in each dimension, made of wood or stone. […]

It seems to me that, at least by my understanding, that is the physical size limit of this pocket plane. It isn’t meant to be extended, or else the spell will have mentioned what happens when you dig through the wood or stone lining the demiplane.

However, the earthquake spell says:

You create a seismic disturbance at a point on the ground that you can see within range. […]

Fissures. Fissures open throughout the spell’s area at the start of your next turn after you cast the spell. A total of 1d6 such fissures open in locations chosen by the DM. Each is 1d10 x 10 feet deep, 10 feet wide, and extends from one edge of the spell’s area to the opposite side (emphasis mine). A creature standing on a spot where a fissure opens must succeed on a Dexterity saving throw or fall in. A creature that successfully saves moves with the fissure’s edge as it opens.

What would happen to a demiplane created by the demiplane spell if fissures opened on its floor due to the earthquake spell? Would the demiplane itself be destroyed? Or would it create a deeper floor in the demiplane? Is this a case where there isn’t enough RAW to say with certainty one way or the other, and that it rests solidly in DM fiat territory?

Is the space inside a demiplane considered “outdoors” for the purposes of Control Weather?

The demiplane spell creates a door that leads to another plane of existence:

You create a shadowy door on a flat solid surface that you can see within range. The door is large enough to allow Medium creatures to pass through unhindered. When opened, the door leads to a demiplane that appears to be an empty room 30 feet in each dimension, made of wood or stone. […]

It seems that this room is the entirety of this plane. There is nothing beyond the ceiling, floor, or walls. In a sense, the ceiling is the limit of the “sky,” although if it has weather is questionable.

Given all this, is the space inside a demiplane considered “outdoors” for the purposes of the control weather spell? Control weather requires that:

[…] You must be outdoors to cast this spell. Moving to a place where you don’t have a clear path to the sky ends the spell early.

Could a significantly powerful caster use create demiplane, permanency and astral projection to gain nigh-immortality?

A scenario for a villain I came up with at one point was an insanely powerful mage who keeps her real body in a demiplane with the timeless trait. In order to beat the heroes she only sends astral projections of herself and since she’s so strong no amount of killing astral projections will stop her. The only way to beat her would be to find the coordinates to her demiplane and kill her there on her own terms. Ignoring whether or not this would be fun, since making an op nigh immortal caster as the BBEG would be difficult to pull off without becoming extremely obnoxious, would it even be remotely possible in Pathfinder lore? I mean could an NPC be even powerful enough to negate the repercussions of having an astral projection destroyed multiple times? Assuming they are not a god or similar being. I can figure out the exact details after I’ve confirmed it’s even possible.

So what would I be able to do to make the 30 feet of demiplane into a true home base? [duplicate]

This question is an exact duplicate of:

  • What permanent spells would I be able to cast to make an extraplanar structure? [closed]

So this character is a lvl 20 hexblade warlock in this situation and I have my 8th level mystic arcanum as demiplane. The dm will probably let us learn any spell regardless of class as long as its not too op. We have a absolute massive amount of money so that wont be a problem. The thing I plan to use the “Base” for is a living space, storage for magic items storage for our mech suits (dont ask, a library since we are dumb and need it, all the other normal house things. It could also be like a war bunker. I am thinking something similar to Mordenkainen’s Magnificent Mansion but permanent. Is there anything I could do other than building it to accomplish this?