Dungeons & Dragons uses many similar words to define the place where things go when they’re not stored here:
- Nilspace: extra-dimensional space, non-dimensional space
- Bag of Holding: non-dimensional space
- Heward’s Handy Haversack: like Bag of Holding: non-dimensional space
- Saddlebags of Holding (Dragon #208): As Bag of Holding
- Hat of Holding: nilspace
- Hat of Holding (Dungeonland EX1): extradimensional space
- Portable Hole: extra-dimensional hole opens to non-dimensional space
- Bag of Devouring: extra-dimensional
- Rope Trick: extra-dimensional
- Phase spider: shifts out of phase; etherealness will put user into the same phase as the spider, so clearly they go to the Ethereal..
- Leomund’s Secret Chest: Ethereal plane
Time to examine what all of that might mean. The most interesting point available for analysis is the effects of the intersection of the Bag of Holding and the Portable Hole.
The Bag of Holding (and all of the associated Holding items, like Saddles of, and Heward’s Haversack): If overloaded, or sharp objects are placed within so as to pierce it, the bag will rupture and be ruined, and the contents will be lost forever in the vortices of nilspace.
If a full Bag of Holding is placed in an empty one, only one more small (ring-sized) item could also be placed in the second bag. Since all Bags of Holding are made by the same sort of magic, they do not work in their normal fashion with respect to other bags. So, once a full bag is placed in an empty one, the second one becomes full also, except for the single, small extra item that may be fit inside it. — J. Wells, Dragon #46.
Portable Hole: A Portable Hole opens on its own particular non-dimensional space. If a Bag of Holding is placed within a Portable Hole, a rift to the Astral plane is torn in the space, and the bag and the cloth are sucked into the void and forever lost. [In this context, the “void” must be the Astral plane.]
If a Portable Hole is placed within a Bag of Holding, it opens a gate to another plane, and the ‘hole, bag’ and any creatures within a 10′ radius are drawn to the plane, the Portable Hole and Bag of Holding being destroyed in the process.
The contents of a pierced Bag of Holding end up in the “vortices of nilspace“. If a Bag of Holding is placed inside a Portable Hole, then everything goes to the rift to the Astral Plane. If a Portable Hole is placed inside a Bag of Holding, it opens a gate to another plane, and everyone w/i 10′ is sucked in. Three different possible outcomes. Simple enough. For the first, the stuff is destroyed. In the second, it’s lost on Astral. For the third result the party itself is dragged along.
A Portable Hole is built from webs of a phase spider (Ethereal) with strands of ether and beams of Astral plane luminaries. The MoP references: “Legends speak of a plane far beyond known routes, the home of all the extra-dimensional creatures that we believe to be bags of holding and bags of devouring” in the section discussing the Ethereal plane as a possible Ethereal Item in the Deep Ethereal. If the Bag of Holding is towards the Ethereal and inner planes, and the PH is towards the outer planes (and Astral), that could explain the extreme results when you put the two together.
The MoP further says the Deeppockets spell uses extradimensional space and cannot be cast in the Astral plane (which would make sense if the extradimensional space was Ethereal).
Girdle of Many Pouches: This broad waist-belt has eight small pouches on its inner front area, with seven others “behind” each of the eight apparent ones, each similar to a Bag of Holding.
Heward’s Handy Haversack: Two side pouches, each similar to a Bag of Holding. Extrapolating, the large central portion likely functions the same.
In rare cases it is possible to reach into nilspace and non-dimensional space from a second connection. This is likely the source of the items in Zadron’s Pouch of Wonders (Dragon #62),a sort of magical grab-bag inside which a great variety of magic items can be found. Examination will reveal that the pouch contains some sort of small object. To utilize the magic of the bag, a character must open the pouch and draw the item out.
When in Astral space, certain devices that use extra-dimensional spaces to store items will expand abruptly so that the exterior of the container conforms to match its interior capacity (Bag of Holding, Portable Hole). Dragon #67.
Rope Trick: one end of the rope rises into the air. The upper end is fastened in an extra-dimensional space.
Bag of Devouring: This bag appears a Bag of Holding, but is the lure used by an extra-dimensional creature. Any substance of animal or vegetable nature is subject to “swallowing” if it is thrust within the bag.