Long ago I had a 2E world that I called Warped World. However, that world originally started as something else, and it has now become what it was intended to be (i.e. Time of Ages). Yet, the idea of Warped World has stayed with me, and now i have created a new map for a newly revised version of Warped World.
My Comments from Facebook
1) For Spelljammer, think of it like this: Warpedspace would have a crystal shell that is cut in half. The world would sit at the center of the shell on the flat part of the shell. The ocean covers the entire bottom of the shell. There is not true void. The entire shell is filled with air, although at the outer edges the air would be so thin that it would be nearly impossible to breathe. The world’s sun and moon rise and set like normal, but where they go is a mystery. Or, instead, the sun sits at the highest point in the shell and doesn’t move. It just dims and brightens based on the time of day. The moon would rotate it. (I think I like the second option better. Opinions?)
2) At the edge of the system/shell, the water doesn’t really end. Travelers simply pass into the planes. I haven’t decided exactly how it will work, yet.
3) Here’s some tidbits about Warped World from my homebrewed worlds index thread on The Piazza: Warped World will use psionics (unlike The Second World); it will also be highly magical and very bizarre. I’m thinking that I will use many of the rules from the Player’s Options books. Regardless, I foresee a world with dozens of playable PC races and an wide choice of classes and character kits. Standard is not a word I am going to associate with its design.
Strange mechanical devices will be the norm on Warped World, as will anything else that breaks the mold of D&D. Weird is not abnormal on this world. As one travels away from the core, the world becomes more planar. Outsiders and elementals become more common. Standard humanoids become a rarity.
4) I kind of want the world to be semi-demiplanar. So, I’d like to keep the neverending sea, but perhaps that sea isn’t visible from the air. Yet, your extra-planar underside idea has merit. Perhaps, when heroes descend into the underdark, they come out on the other side, but it’s another plane of existence. It would be the division between heavenly planes versus hell-like planes. The seaway planar boundary leads to the high planes while the underdark side is the low plane.
5) The low side would have a void sky. No air. A burnt out sun. Shattered moons.
6) FYI… I see the shell as being relatively small. The area beyond the normal atmosphere would be an aether-type space. It would look space-like but it would be ‘pulpy.’
7) Link: Aether (classical element)
8) A spelljammer in Warped World’s aetherspace would move like in wildspace.