The Stybius system is all that remains of what was once a red giant star and four planets. When the star expanded and then contracted into its current state - a tiny white dwarf - it destroyed its satellites and reduced them to radioactive waste; the remnant of one such planet is what is now referred to as 'Stybius'.
So radioactive that it perpetually glows green, the planet - or, rather, the stunted molten remains of what was once a planet - provides a very dull glow to the rocky debris floating within the vicinity of the planet. Both Stybius and its wide-spread asteroid field are mineral-rich, though the most abundant of these, Indescribium, is a relatively common and not particularly valuable one.
However, while the asteroids have been mined for centuries, currently only a largely automated group of semi-sentient excavation droids remain, having slowly eked out billions of metric tonnes of rock from the asteroids, leaving strange but perfectly-shaped hard-edged asteroids in their wake; everything from hexagonal blocks to tetragonal carved lithoforms to pyramidal structures have been designed by the droids, often with their own intricate and highly patterned structural layerings and carvings; others are hollowed out entirely or perfectly circular.
Stybius is on the Outer Rim.