Just an idea for a D&D campaign I'm working.

Spelljammer Gen-SX

Over a thousand years ago the Spelljammer met with a mysterious and explosive end. The Phlogiston as many had known it was no more and all the known crystal spheres shattered as one, instead starships plane shift to the astral plane, hereto referred to as the astral ocean, and can be accessed by sophisticated enough vessels finding that the crystal sphere didn’t really go away but evolved into something weirder. Slowly but surely the universe rebuilt itself.

Weird things called “solar systems” developed as technology sort of caught up with magic and a strange kind of courtship began. But the more things change, the more they stay the same. Mind flayers from many solar systems banded together to create the Illithid Imperium and gathered to themselves many beings to serve them willingly, as in the case of the neogi, and not so willingly. And they are not the only ones as a hobgoblin with a golden skull mask named Rathus managed to gather to his banner all manner of goblinoid races and took over the orcs as well, including the scro much to their chagrin, and managed to breed the orc into a new, goblinoid form and thus forcing them into the fold of the Hobgoblin Empire.

One such solar system is where the campaign will begin and is based loosely on our only solar system although there are only six rather than the nine planets of our solar system. Where Mercury and Pluto are in our solar system are two more asteroid fields and there are three suns: one red giant, one white dwarf and one black dwarf which the residents refer to as the “Eyes of the Solar Emperor” a nebulous and uncaring deific entity who supposedly uninterested in worshippers. The third party worlds of Vodari, Midgard and Alessia occupy the spots Venus, Earth and Mars do in our own solar system with Jupiter, Saturn and Neptune replaced by the worlds of Olympus, Shangri-La and Valhalla; Olympus and Shangri-La are exactly like Jupiter and Saturn in our own solar system but Valhalla is a little…different; you see Valhalla has a crust of ice about a hundred miles thick with cold water and a planetary inner sun at its core which is completely surround by said water.

The three asteroid fields are referred to locally as Hearth Fence, the Inner Limit and the Outer Limit with the Hearth Fence situated between Red Eye and Vodari, the Inner Limit is between Alessia and Olympus and the Outer Limit is just beyond Valhalla. The Hearth Fence is believed to keep Red Eye from expanding any more than it already is which the residents of all three inner circle planets are most grateful for. The Inner Limit is to keep the folks from the front track of planets from meandering into the back track and the Outer Limit is to make sure everything is more or less contained although there is a gate here to the astral ocean which is not well known and that is supposedly by design.

Of the three worlds, Alessia is the most technologically advanced followed by Vodari and then Midgard as the folk of Alessia have figured out how to created airships and space ships as well discovering the Kanji-Rune Gates and figuring out just how they work. Kanji-Rune Gates are basically star gates with portals allowing travel throughout the solar system and beyond if one knows the right combination as you key in components from an astounding list of characters that look like Japanese kanji and Nordic runes thus giving the devices their collective name. Alessian starships can invoke these same gates to bypass the Inner and Outer Limits creating a wormhole large enough for the ship to pass through in terms of bypassing the Inner Limit and opening a portal to the astral ocean in regards to the Outer Limit.

In general technology is a weird mixture of steampunk, dieselpunk and atompunk with zeppelins and submarines existing in abundance along with more advanced craft. A word on helmsmen, in spaceworthy vessels there is a place for a helmsman but while the helmsman can guide a given ship as if it were his or her own body, the problem is in order to become a helmsman you literally must merge your physical body with the ship you are guiding, think Pilot from Farscape and you have a pretty good idea as to what is involved in becoming a vessel’s given helmsman. More often than not this involves transferring one’s consciousness into a specially manufactured construct or golem created for just this purpose; alternatively with gear forged and war forged helmsmen they have their very bodies bolted to the ship or otherwise plugging themselves in and thus being able to utilize the function of the vessels through the same neurological process that you and I control our own limbs.