This is a very dumb origin idea. Basically, your empire was connected to an ancient battle which saw the destruction of your entire civilization, besides your homeworld. It is now a (somewhat) stable fractured world, with a few starting deposits to enable basic alloy, mineral and energy production. Your species could (should) have a starting trait which is something like 'unbelievably resilient', providing +20% habitability and +50% army health for your species.

It should be purposefully terrible, with the only guaranteed world near your system being the other fractured world with the dig-site on it.

That's it. Its probably the worst start for an empire possible, and it should be. No faster dark tech, no ships (other than the dig-site next door) nothing, other than the decent starting trait.