Editing Demiplane (section)

===3rd Edition===
Demiplanes made a definite comeback, but there was a lot of weird stuff throughout the edition.  The first appearance was in the 3.0 Manual of the Planes: the Planeshifter prestige class gained access to the ability demiplane seed at 10th level.

The next mention of making demiplanes was in the Epic Level Handbook, under the ''genesis'' 9th-level spell, available only to wizards or clerics with the Creation domain (until the domain was reworked in 3.5).  It was costly at 5,000 XP and a week's casting time (8 hours/day), but you didn't have to take some arbitrary class to get to it; it still had to be done on the Ethereal Plane as in 2nd edition.

In 3.5, ''genesis'' was also made a 9th-level psionic power, restricted to Shaper psions, who got it for a much less stringent 1,000 XP and could be created on the Astral Plane.  

Oddly, there is one final source for creating a demiplane: the 9th-level general cleric spell ''Word of Genesis'', which had a truename component (basically, you had to buy ranks of a specific unique skill and pass a check at DC 50; yeah, it was about as [[Skub|well-written]] as the rest of the Truenamer section).

It should be noted that you don't really have to use such powerful magic to get yourself a little pocket dimension, at least temporarily.  Rope trick has long been regarded as an infinitely useful "rest area" spell in dungeons, and ''Mordenkainen's magnificent mansion'' is even better, giving access to plenty of food and space for various tasks (along with a very long duration at the time you get access to it).  In fact, there is a somewhat obscure reference in Complete Scoundrel to a permanent ''mansion'' effect (the headquarters of the Blind Tower criminal organization); given that the ''permanency'' spell even mentions that you can research certain spells to be made permanent, and that it costs a pretty pinch of XP to make any high-level spell permanent, it's not a far-fetched notion for a DM to approve such a thing.  But there is a downside: the thing can be dispelled, causing all the contents - and guests - to spill out of it, so be advised.