I had had the impression from reading about it before, that the Elemental Plane of Time is a demi-plane (and distinct from the Temporal Prime). However, this weekend at a gaming convention I got a look inside Manual of the Planes, which states that the Plane of Time is infinite in size and is an inner plane. This was part of a section on alternate cosmologies that don't fit entirely with the traditional Great Wheel. So I'm wondering, what other books mention this Plane of Time, and do they list it as elemental or demi? In particular, do any Planescape sources mention it or indicate how it would fit into the Great Wheel cosmology? And what about some other weird Elemental Planes I've read mention of -- Psionic and Gravity? Does anybody know any more about these strange things?
the Plane of Time and other bizarre elements
I'm at least under the impression that almost any material concept can be the core trait of a demiplane. There's a demiplane of Electromagnetism (although it's being swallowed by the Quasielemental Plane of Lightning).
A demiplane of Gravity might be have been eaten by the Plane of Earth, which includes concepts of "heaviness," but it might also stand alone. A fun version of the plane might be one where "down" was almost completely random, so that someone falling through the plane (which, of course, has little else in it) would tumble not in straight lines but in zigzagging arcs as he falls through directed gravitational fields, eventually ending up orbiting somewhere or oscillating across two fields lying counter to each other.
Alternatively, everything might get sucked toward one point, leading to an accumulation of stuff there. It might be profitable to dig through this mound of stuff... if you don't get crushed by something else falling on you to add to the pile! Or crushed under your own weight as the gravity varies randomly... or sucked across dimensional barriers when the Negative Energy Plane flares up and the core of the mass becomes a black hole... :^)
In Dragon #353 the 2e Demiplane of Time and the 3e Temporal Energy Plane are described as being the same thing. I only had a single line to describe it however.
Like Rip, I personally view the (demi)Plane of Time as being infinite in size, but floating in the deep ethereal. Externally bound by the ethereal mist, yet infinite in interior size.
I've used the place once or twice, but never to a great amount or for very long (because it's incredibly hostile to PC travel).
In the 2e Chronomancer sourcebook, "Temporal Prime" is a "pseudo-reality" that intersects all planes of existence.
In A Guide to the Ethereal Plane and Planes of Law (and in the 1st edition Manual of the Planes) there is a "Demiplane of Time." This demiplane is located in the Deep Ethereal with the other demiplanes, and nearby, in the ethereal, grows a kind of plant called a chronolily.
The Monstrous Compendium Annual Volume Three lists the temporal creatures from Chronomancer, transplanting them to the Demiplane of Time instead.
I'm personally inclined to make the Temporal Energy Plane a full plane, but I would put it in the Deep Ethereal with the demiplanes. It's just a demiplane that has become infinite as it developed.