A friend of mine emailed me this to me back in 2013. He got it off of a forum thread on Planewalker.com.
A quick glance at Wikipedia reveals to me that there are two different interaction systems: one "generating", in which one element creates another, and one "overcoming," in which one element lessens another. Instead of having quasi- and para-elemental planes, then, perhaps you could have more dynamic Generating and Overcoming planes, combining aspects of the quasi- and para- divisions.
Picture, then, the five elements arranged in a ring: Wood, Fire, Earth, Metal, Water. On the pole above them is Yang (positive energy) and on the pole below them is Yin (Negative Energy). Truth to tell, of course, there's no such direction in the ethereal: every elemental plane in this arrangement shares a border with every other elemental plane, even Wood with Earth and with Metal. You could arrange the ring Wood, Earth, Water, Fire, Metal, and in so doing more clearly show the arrangement of Overcoming planes, which normally have to be shown on a
separate map for two-dimensional mapmakers, or hung between the planes in the shape of a pentacle for three-dimensional orreries.
So we'd have the following ten, oh, let's call them hemiplanes:
Generating Hemiplanes:
Wood generating Fire: Hemiplane of Air. Winds rustle through reeds and shake branches as you pass toward the plane of Fire; gradually, the winds become faster, the grasses dry out, the branches rub harder... and then they burst into flame all around you. (There seems to be a large inhabited portion of this plane far away from any wood at all. How very strange, think the wu jen.)
Fire generating Earth: Hemiplane of Coals. Follow the cinders as they collect, from specks into rivers of red-hot boulders, cooling and solidifying into a wall in front of you. Rich ash fertilizes the soil that surrounds you, volcanic obsidian glimmers. (Negative energy? When ash is so good for plants and volcanos create whole islands? What strange notions foreigners have of the elements. This plane is touched by Yang, not Yin.)
Earth generating Metal: Hemiplane of Ore. Gems are pretty, yes, we see why you call this the Plane of Mineral, but really, ask any dwarf and he'll tell you it's the veins of metal he's after here.
Metal generating Water: Hemiplane of Rain. Down it pours from pure Yang, gentled into droplets by the elemental nature of Water, to be collected here by Metal and poured into its native plane.
Water generating Wood: Hemiplane of Muck. Yang enriches water with nutrients, which thicken until you slow from swimming to a crawl through mud and lush soil oozing with vitality, to emerge in the great forest of the Plane of Wood.
Overcoming Hemiplanes:
Water overcomes Fire: Hemiplane of fumes. You can get from Water to Fire, if you're willing to pass close to Yin, and go through a choking hemiplane of gradually dirtier steam and smoke to get straight to your destination.
Fire overcomes Metal: Hemiplane of Magma. Metal in this plane has fallen under the relentless assault of fire. It may be a necessary step in the process of purification, but the wu jen can be uncomfortable so near a manifestation of Yin. (Even if you don't think the plane is near Negative Energy at all.)
Metal overcomes Wood: Hemiplane of Vacuum. To travel from Metal directly to Wood, you must pass in the track where the blade has struck, through this plane the wu jen call the Wound. Launch yourself from the point of the metal's wedge; if you know the way, you will land in a notch of wood on the other side.
Wood overcomes Earth: Hemiplane of Dust. Travel to where the forest thins, where Wood has taken the nutrients it needed from Earth, and in this border region you see the dry, lifeless dust that is left behind. To dig down here is the fastest route from Wood to Earth, but don't hope for a pleasant trip.
Earth overcomes Water: Hemiplane of Salt. If you must cross the abyss between Earth and Water without passing through Metal, you will pass through the realm where the Earth has sucked up the water that reached it.
