Quote Originally Posted by Hannibal78 View Post
It's entirely up to the DM, how he rule the vessel. There are some differences but also there are some connection between an extradimensional space and a Demiplane.
Every demiplane is an extradimension, but not every extradimension is a demiplane.
Now, every demiplane can has it's own rule. A demiplane can be as small as a room, or as big as a continent or province. Ravenloft and the rest are Demiplanes. Bag of Holding no problems.
You can travel to a demiplane with certain spells, items and abilities.
Now cuz you are using the genie ability, what they give to the character, this is more similar for me for a Demiplane.
And also, i don't think it's fair to the player to cause such pain in the ass with a bag of holding.
Bag of holding, after a certain lvl for a party is relevant, at least one almost always you can find in the possession of a party.

So in my opinion its just fair to say, the vessel is a demiplane, specific rules, which mean you can use your bag of holding or similar item without any problem, cuz the simple extradimension problem not apply.

Btw, if you are in your vessel, and you have the plane shift spell, you can use it, and go back to the material plane anywhere where you want (even of the DM rule that the vessel only an extradimensional place).
Also with that spell is possible (discuss with the DM) to go into your vessel, without the time limit. The extra healing option and the fast short rest option, you should discuss with your dm, how it's working.
If the DM rule, that is working only cuz of the lvl 10 ability, then you can use only that way.
But if the DM rule, that these effects part of the Demiplane (vessel) then you can use anytime, doesn't matter how you or your company will visit the place.
Don't forget to ward your vessel when you can, and especially if you are making a material component for your Plane Shift spell to access to your vessel. If you loose, other can infiltrate into your home.
Your misconception is in the wording. A Demiplain and a Extra Dimensional space are different things. There are spells and items that use the wording Extra dimensional space like Bags of holding, rope trick, Genie vessel, mordakien magnificent Mansion, pact of the blade. Then there are other spells, abilities, item that use the wording Demiplane like Demiplane, find familiar, sorry they are the only things I can find or remember that have the wording Demiplane.

My point is a demiplane and extra dimensional space are two different things.