Pygons

The universe is unimaginably ancient.
Long before the modern space-fairing community began to touch the stars, there were others who travelled the cold, dark, depths of space. Sometimes called "the Ancient Ones," these Pygons visited many worlds in Pavo Dioscuri. Hating bright light, they dug into the planets they visited, leaving labyrinthian dungeons in their wake. 
No living Pygon has even been witnessed in the modern era. Only their art and ruins give any indication as to their appearance and culture. They seemed to be strange masses of flaps and ropy tentacles. At their centers was a toothy, probelike mouth.  
They were masters of travel magic. Their ships did not seem to employ Energized Malachite spelljamming. While no intact example of their space-fairing technology has been discovered, a bounty in the tens of thousands has been outstanding for generations.