D&D 5E What demiplanes have been described in D&D? Inspiration for Acererak's phylactery location

[Urriak Uruk]

Hi all, so I'm DMing a game of Tomb of Annihilation, and <don't read further if afraid of SPOILERS> that adventure ends with a fight with Acererak, the lich behind the death curse.

Even if the party is victorious and bests the lich, he can't be killed permanently because his phylactery is located on an unknown demiplane.

Now knowing my party, the idea of letting the villain just slip away is a big no-no. So no doubt when they best him, they'll soon be on the hunt for the location of his phylactery. I could just make one up from scratch, but I thought it might be fun to learn more about published demiplanes.

So my question is, what demiplanes have been described throughout different D&D sources? Literally any source, including Dungeon/Dragon magazines, across any edition, is on the table. What isn't on the table is something that isn't a demiplane, like the Outer Planes, Elemental Planes, Shadowfell, Feywild, etc. I'm looking for planes that are smaller and aren't one of the big major planes we hear of often in D&D cosmology.

Also, I know the Tomb of Horrors is the obvious location for Acererak's phylactery, but I'd like to save that for the final confrontation with the lich once his phylactery is found.

 

[Enrico Poli1]

Demiplanes are "spaces" within the Ethereal Plane, that can be very very different. They can be large as a room or as an entire world. A wizard that creates a Demiplane can impose a number of rules: for example no gravity, time passes x10, no need of air, exit only with conditions, magic null zone, and so on. Also, entering a Demiplane could be difficult, for example with a Plane Shift spell and a secret forked rod (the secret of which must be obtained somehow). If an Archlich creates a Demiplane for his phylactery, it's deadly, and the object is well hidden.
Anyhow, the most famous Demiplanes in past editions were the Demiplane of Shadows (later replaced by the Shadowfell) and the Demiplane of Dread, a prison Demiplane known also as Ravenloft.

Edit: to have a good example of Acererak Phylactery's hidden place, look at Return to the Tomb of Horrors; then you'll have the scope of the Power of the Archlich.

 

[Nebulous]

and the Demiplane of Dread, a prison Demiplane known also as Ravenloft.

I was going to say Ravenloft. You could have an interesting crossover campaign with Strahd and one of the items that can kill him actually being the phylactery shapechanged into something, and you have to kill Strahd to even get OUT of Ravenloft to destroy the phylactery.

 

[LuisCarlos17f]

I found this:

Codex of Demiplanes | Planewalker

mimir.planewalker.com

 

[Blacksad]

There's a few in a guide to the ethereal plane (2e) Dungeon Masters Guild and at least one in the vortex of madness and other planar perils (2e) Dungeon Masters Guild the 3e manual of the planes recommend using them for dm specific cosmology (wizard closet, sealed realms)

 

[Jfdlsjfd]

With 27 INT and 21 WIS, Acerak is one of the smartest guy around. His goal is to protect his phylactery at all cost. Electing to make it sit in an inhabitated area, even by monsters or by Strahd, is not smart. A wandering party of adventurers could stumble upon it while on the plane of Dread and say "hum it's a phylactery, let's destroy it because no good think can come out of that thing..." Or allow the Dark Powers of Ravenloft to take it and use it as leverage against him. Putting the phylactery in a place where geological hasard can destroy it is not smart as well (OK, there is a chance in a million of an earthquake of huge magnitude, but if you're playing the eternity game you know that with enough time, it is absolutely certain that a very improbable event will come to pass). Placing his phylactery in an interesting demiplane would be a mistake.

So, even if it is not conducive to an heroic adventure, Acerak should probably have cast demiplane to create an empty 30x30x30 room, protect its phylactery against heat and pour molten lead through the door to fill most of the demiplane with it (with just enough space for his body to reappear and for an interloper to stand right on the zone when the glyphs of warding are taking effect.. Most spells (scrying, find the path...) don't work to access extraplanar locations. Access will be extremely restricted. Even if Acerak was magically compelled (or tricked) to divulgue the location of the demi-plane, the amount of lead to search for would give him some time to react. Of course, Acerak would have created over time 83 identical lead-filled demiplanes in case someone tried to get information on this plane thorugh yes/no answers through a Contact Outer Planes spells and get enough information to become familiar enough with the plane to attempt to demiplane into the correct one. And on the other hand, he would have publicly created 7 uber-phylacteries of insurmountable power that would be sent on Ravenloft, the plane of Shadow and so on, just to act as decoy (simply enchanted with a spell of alarm to know when and adventuring party is determined enough to kill him to enter Ravenloft just for this task, so he can preemptively scry over them and murder them by attempting an alpha strike).

Fortunately, Acererak turns to dust and leaves no body behind that could be interrogated through Speak with Dead. He can't be charmed. The forked tuning key to the demiplane could be acquired by a third-party through a wish spell outside of the normal range, but then, such a spell could also be worded to acquire the phylactery directly... If he was truly paranoid, he could forego his single, regular contingency (woe 5e) to have an obscure spell like Shadow of Moil cast on himself with the contingency condition being "a being that is not me enters the demiplane of the phylactery". So if he suddenly finds himself wreathed in shadowflames, he would know it's time to act with decisiveness. Poor Acererak doesn't usually prepare drawmij's instant summon but he could have pre-attuned a sapphire to its phylactery to retrieve it "across any distance and plane" should such a dire event occur...

Due to mebeing a simple level-1 Commoner with average stat, I can't really envision all the step a 27 INT creature could imagine, but it would certainly be along those lines (and taking the time and discipline to actually rotate the phylactery among the 83 demiplanes of lead with some regularity). So the only way to get rid of him would be the 1d10 days between killing Acererak and the reformation of his body.

To make it fun for the players, find a way to impart the knowledge of the epic preparations the lich took with his phylactery, investigate some red herring (like the faux horcruxes) and so on until they cana devise a suitable plan to execute. Maybe involving tricking Acererak into actually Drawmijing his phylactery into his hands just before attacking him.

 

[QuentinGeorge]

Hi all, so I'm DMing a game of Tomb of Annihilation, and <don't read further if afraid of SPOILERS> that adventure ends with a fight with Acererak, the lich behind the death curse.

Even if the party is victorious and bests the lich, he can't be killed permanently because his phylactery is located on an unknown demiplane.

Now knowing my party, the idea of letting the villain just slip away is a big no-no. So no doubt when they best him, they'll soon be on the hunt for the location of his phylactery. I could just make one up from scratch, but I thought it might be fun to learn more about published demiplanes.

So my question is, what demiplanes have been described throughout different D&D sources? Literally any source, including Dungeon/Dragon magazines, across any edition, is on the table. What isn't on the table is something that isn't a demiplane, like the Outer Planes, Elemental Planes, Shadowfell, Feywild, etc. I'm looking for planes that are smaller and aren't one of the big major planes we hear of often in D&D cosmology.

Also, I know the Tomb of Horrors is the obvious location for Acererak's phylactery, but I'd like to save that for the final confrontation with the lich once his phylactery is found.

Actually, if you want the canonical demiplane, it's in the adventure "Return to the Tomb of Horrors". (Moil?) It isn't the tomb itself, but accessible from there. I'm sure the mention in Tomb of Annihilation was an easter egg referring to that work.

 

[Iry]

I placed his phylactery somewhere poetic.
It was a small artifact resting inside a Sphere of Annihilation. This one.

 

[Urriak Uruk]

Actually, if you want the canonical demiplane, it's in the adventure "Return to the Tomb of Horrors". (Moil?) It isn't the tomb itself, but accessible from there. I'm sure the mention in Tomb of Annihilation was an easter egg referring to that work.

I'm actually thinking of using the 4e module "Tomb of Horrors" as that contains several different planes which culminate into a final fight with Acererak.

 

[Coroc]

Technically each bag of holding or portable hole is a demiplane.