Quote from MiniDeathStar >>

Or you could fill it with meatgrinders, spikes, blades, saws and acid, thus creating the Demiplane of Extremely Painful Death.

And then push the evil mastermind into it.

 cast demiplane under their feet

Quote from HailRobonia >>

Step one: cast demiplane on flat surface at the bottom of a large body of water.

Step two: open door and fill demiplane with 27000 cubic feet of water (= around 843 tons of water)

Step three: when you need to flood something, cast demiplane on a ceiling or high up on a wall and let it blast out.

 

 

 why limit your self to water (lava,acid posinius gas)

this is so op

I feel like this spell is kinda underwhelming

Remember that by the time a character is casting this, their feats have likely bought them prestige and allies all over the world. If they cast the spell every day between adventures, they can quickly wind up with a truly massive domain that they can fill with whatever they can get their hands on. And unlike with spells like magnificent mansion, the contents of a demiplane aren't tightly localized figments of reality: they're the genuine article. If you give the party a year before kicking off the multiverse-threatening campaign finale, a wizard with this spell, resilient sphere, and any further form of teleportation will be able to kidnap, breed, and terraform entire ecosystems into existence. Add on plane shift, and the size of the creature you're kidnapping isn't even an issue. Add some modify memory shenanigans and enjoy the chance to play god. 

I mean, I threw this at my players through a DM-NPC, a Half-Orc Necromancer who functioned as their go-to quest-giver at low levels who was testing to see just what sort of character the players possessed.

Using a home-brewed item called the Permanence Stone, he had four Demiplanes in his wizard's stronghold that opened at specific times of day, and required a specific key to actually trigger their opening from the Material Plane side of things.

1st Demiplane was a home-away-from-home, a sturdy tavern-like dwelling divided into two levels, 15 foot tall ceilings, had accommodations to house up to eight people, a fully stocked larder, a bathing hall and a small library and a permanent Teleportation Circle, basically where the DM-NPC would stash NPCs and PCs when things got hairy due to it having a permanent Mordenkainen's Private Sanctum on it, so if you needed to lay low for a few in-game weeks, the players just could get shunted to, or later on, teleport directly to this Demiplane. Opened at 10 in the morning and closed at 11, and you required a silver tankard stamped with the DM-NPC's sigil on it.

2nd Demiplane was a frigid cavern which held three Silver Dragon eggs that the DM-NPC was holding onto as one of his allies, a Adult Silver Dragon, had recently lost most of her clutch to a band of greedy adventurers, and had given her remaining children to the DM-NPC to safeguard while she hunted down the adventurers and made them pay. Opened at 4 in the afternoon and closed at 5, and you required a holy symbol of Bahamut to open it. No permanent Teleportation Circle due to the risk of the adventurers coming back to try and finish the job, and the rush-job required to make the thing in the first place.

3rd Demiplane was the Wizard's private sanctum, where his Clone was stashed as well as his more precious magical items that he didn't want to risk getting stolen by thieves or rival wizards. Much like the 1st Demiplane except only designed to hold 1-3 people, had a much larger library, a permanent Magic Circle in addition to a permanent Teleportation Circle, permanent Mordy's Private Sanctum and a permanent Anti-Magic Field around a fiendish relic he was safeguarding until a more permanent way to get rid of it could be found. Opened at the stroke of midnight and closed at 1, only the Wizard could open it due to it needing him as the key.

4th Demiplane was a prison, three levels, full of individuals the PCs and DM-NPC had captured and were interrogating, or whom were too risky to leave in more mundane prisons. Eventually most were shipped off to more official holdings, but there was, by campaign's end, a high elf assassin, eight human cultists and a very confused yuan-ti pureblood cleric in a anti-magic cell. Again, lots of permanent effects and opened at 3 in the afternoon, closed at 4 and you required a pair of manacles stamped with Tyr's holy symbol to enter.

It served as a great series of props and bolt-holes for the players, it gave them ideas for what would happen if they gained access to a demiplane of their own, and when something could breech a demiplane, they realized just how serious of a threat they were facing.

Love this spell, both as a Forever-DM and on the rare occasions I get to be a player.

Can you use this with glyph of warding?

Quote from BiggieBiggs >>

Can you use this with glyph of warding?

Strictly RAW I don't think so, as a bound spell in a glyph needs to target a creature or an area, which Demiplane doesn't (it doesn't have an area of effect like a sphere, or "all creatures in range" or such). Of course a DM is free to allow it anyway if your goal is just to have a casting of this spell that you can make in advance, with the glyph simply providing you with a way to trigger it?

If your goal is to make it a trap, keep in mind that while you could argue having the door appear on a floor (if it's a flat surface), it's described as a door that needs to be opened, so creatures won't immediately fall through it, and it's not a concentration spell so the door remains for an hour unless you dispel it.

Quote from evilvillans >>

Quote from MiniDeathStar >>

Or you could fill it with meatgrinders, spikes, blades, saws and acid, thus creating the Demiplane of Extremely Painful Death.

And then push the evil mastermind into it.

 cast demiplane under their feet

The entrance to the demiplane is a door that has to be opened; if you can cast it and then get over to it and open it then maybe, but your DM's probably going to want to give the big bad a saving throw or a chance to react, rather than just standing dumbly in place as you open a trap door under their feet 😉

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.

Which means you can just recreate the door that let you into the demiplane you are "trapped" in.

You can connect to a demiplane you have made before (or a new one), creating an infinite loop wherein you exit a door on one side of the room, entering the other door on the other side of the room, cycling round and round like the most pointless Mobius strip ever imagined (and a waste of an 8th level slot).

It says nothing about connecting from a demiplane to somewhere else, like the Prime Material.

However, you should know Banishment, even if you are a warlock, & you are not a native of this demiplane you created just over an hour ago.

Used this spell and inverted Magic Circle to trap an annoying Pit Fiend. Pretty sure he's pissed at my wizard by now.

Not just the demiplane spell.. but they need to be familiar with the demiplane you created in order to open a door to that demiplane. Right?

 Interesting

Quote from HailRobonia >>

Step one: cast demiplane on flat surface at the bottom of a large body of water.

Step two: open door and fill demiplane with 27000 cubic feet of water (= around 843 tons of water)

Step three: when you need to flood something, cast demiplane on a ceiling or high up on a wall and let it blast out.

 

 

 I’m having people in my setting do this now, thank you!

You could cast Banish on yourself but then you dont know where you end up. It just says material plane.

I am now taking prisoners 

Ok, nitpicky comment; It states that when you use this spell the room appears as an empty room no larger than 30f any side.  Does this mean that, as written, if you trap someone in the room and attempt to re-summon the same room it would: 1 Spell Fails - 2 Delete the person inside - 3 Summon a new very similar but empty room?

It does say that if you know the content of the room you can connect to that room, the thing with living beings however is that they have the annoying habit of changing their environment, even unintentionally...  Such as evacuating waste or stabbing a wall.  How precise does your understanding of the room need to be to reliably connect to it?  And is this a great concept for a horror adventure? <- my IP ;)

No. It can do two different things:

1) Create a new, empty demiplane

2) Connect you to an existing demiplane (if you meet the necessary requirements to achieve this). I'd say the level of knowledge needed is fairly high (can't just be 'a storeroom full of stuff' but also can't be too absurdly high such that a fly getting in while the door's open for an hour without you noticing means you lose all your stuff). I'd tend to rule that unless some third party broke in without your knowledge, you were able to reconnect to a demiplane, even if a prisoner may have broken some ropes, or chains, or whatever. However, if they were able to escape somehow (banishment/plane shift/whatever) or bring in help, then the spell would fail as that would change not merely the shape of what was in the demiplane, but it's actual contents. 

Quote from Twilightofinfinity5 >>

Yep this is gonna be in my interesting Drifter Class
Drifters are known for their great soul and spirit, hopping through planes, terrains, and teleporting to a known place as home. These humanoids learn the rightful path and art of their Drifter Order and assemble a symbol of spirit.

when this gets finished, is there any way I could check it out? sounds really cool.