Ways to enter extradimensional spaces

[Raunchel]

Today I was thinking about defending a place and ran into a little problem. I thought about getting a bunch of enveloping pits to build my base in, entered from a small stronghold from the stronghold builder's guidebook. But I found myself wondering about the defenses I should put into the pits. Can they be scried into, or could someone planeshift into them?

[Phelix-Mu]

Pretty sure the rules don't say much on this point, as they actually are pretty sparse on the details of how extradimensional spaces works at all. I'd advise discussing it with a particular DM, as I've seen some reasonable arguments for allowing some forms of magical entry to enter them. The basic issue is does it count as some kind of "plane."

Also, the transport clause of wish is pretty iron-clad, and you would do well to have your own contingency/contingent spell item up to allow you to celerity in response to the appearance of someone in you domain, as alpha strike archmages can ruin pretty much anyone's day.

Finally, search for "extradimensional space" and "nondimensional space" here on the forum. Several long threads that I'm not quite remembering at the moment involved some pretty extensive discussions of just what the rules do and don't say about this stuff. I posted in several of the threads, but I can't quite recall who started them.

[Zilzmaer]

For what it's worth, I believe the standard rule is that extradimensional spaces use a portion of the Astral plane, but I can't find my source on that.

[unseenmage]

I know I replied to one of these threads once with evidence from Manual of the Planes and where that info was copy pasted into both the 3.5 DMG and Planar Handbook showing that extra dimensional spaces are considered demiplanes. Sorry I can't give you more. Am on mobile & afb at the moment.