Thr original sith world, Korriban. Primordial, hundreds of thousands of years before the battle of Yavin. Primordial, earthily insectoid feel. Pureblood sith, the leathery faced, anntennaed, force-sensitive, ruthless creatures. Not yet connected with the rest of the galaxy.  Like a tribe, a tribe in a region of scarce resources. The Sith reveal, revel in emotions, but these Sith would be at their most nakedly ambitious, barbaric, paranoid, desperate and cruel.

Perhaps the technology could be lessened, but not completely  to an equivalent of our level. Everything steeped in magic, the occult,  random violence, bangs and subterranean wrigglings.

Nortt and Moevott

Inhuman evil, treblinka, magma grinding in sooty dark.