So this is how I see the premise of Firmament, viewed through the lens of 4E.
The PCs are some contemporary people who accidentally reach up one night and grab a star, pulling themselves adrift in the void of space. After wandering alone for a while, they are eventually recovered by a small settlement of other people who had similar accidents. Theirs is the only active human settlement among the stars, but there is archaeological evidence of one or more historical human civilizations in the distant past.
There are three classes, based on three modern interpretations of lost arts once known to the ancients.
One class focuses on gathering and channeling the mystic (well, primal, really) power of the stars, the power that enables humans to live in the void of space and travel between the stars. This class is basically a laser cleric.
Another class focuses on body movements, the ancient and contemporary dances that map travel between stars, a combination of choreography and cartography. This class marks opponents like a fighter, flits about the battlefield like a ranger, and shifts opponents and allies around like a warlord.
The final class is composed of people who’ve been exposed to the Cthuloid dark forces that exist in the void of space, between the stars, and have been corrupted by it. They are both sneaky like a rogue and have dark, mystic abilities like a star-pact warlock. You can also gain levels in this one if you’re lost out in space too long, but I think they replace your existing levels of whatever other class you are.
The enemies most commonly encountered are shadows, which are the lesser minions of the dark Cthuloid forces and are most likely the ancients themselves and other more recent human travelers who have been corrupted by them until they are alien, ephemeral beings. There are also bigger shadows that were most likely never human at all. Most of them are re-skinned undead. Shadows can only be directly harmed by radiant damage, something that all three classes (especially the laser cleric) can do, but all radiant attacks draw on a precious resource: characters’ hit points, which represents the amount of star energy they have absorbed. Run out of hit points and you’re mostly likely going to be captured by the shadows and corrupted until you become one of them.
Consequently, encounters involve a lot of things that aren’t direct assaults on shadow creatures (though there’s some of that as well). Running away is a common goal, which usually involves getting everyone to a place where you can see the night sky clearly. Also, since players are often sneaking around the ruins of the ancients, looking to unravel their secrets, there are a lot of skill rolls that will happen on the battle map, activating ancient defenses or quickly trying to find secret exits. Of course, as contemporary people, PCs begin with the wrong skill sets for this kind of work, being farmers or computer programmers or what have you. But there is a system by which the skill sets the characters begin with are gradually converted to skills that are actually useful out here in space.
Unlike most 4E stuff I’ve seen, the difference between being on the battle map and just rolling skills and skill challenges will be less dramatic, or at least there will be more middle ground between them where interesting stuff happens.
