Talos is a world shrouded in mystery. The earliest documented account of the system dates from a Sword Worlds survey expedition that visited Talos in -147. The scouts found evidence of sophont habitation in the form of highly-distorted, undecipherable radio signals. However, no further details could be learned because a massive (50 kiloton?) bronze-colored spacecraft of highly unconventional design that was in orbit around the planet moved to intercept and fired warning shots every time the survey ship attempted to approach. It was also evidently jamming all transmissions to and from the planet.
There is a break in Sword Worlds records, but Darrian archives indicate that the mysterious vessel was still standing sentry over Talos in Imperial year zero (0). However, by the time that the first Imperial scouts visited Talos in 151, the strange spacecraft had disappeared. The planet proved to be inhabited by what at first seemed to be an entirely unremarkable human population of about 250,000 that was living at TL–7.
The Talosians were entirely ignorant of the fact that a huge, alien craft had once orbited their world, and knew very little of their own history. 
The Sword Worlders had speculated that Talos was a Darrian colony that had become isolated after the Maghiz, but the Darrians themselves rejected this theory because the mysterious spacecraft bore no resemblance to any known Darrian design. When contact was finally made with the inhabitants, they were found to be genetically distinct from Darrians, Solomani, Vilani and Zhodani alike, and spoke a language that appeared to be entirely unique and unrelated to any other known human tongue. This has prompted most experts to theorize that the Talosians are the last survivors of an unknown spacefaring culture that had arisen somewhere in the Trojan Reaches and disappeared before the era of the Sindalian Empire (-2074 through -1441).
The ‘Riddle of Talos’ was of interest only to historians and linguists until 708, when the mysterious vessel inexplicably reappeared, and resumed its former habits of intercepting all ships that attempted to approach the planet. It took nearly 100 standard days for the Imperial bureaucracy to make up its collective mind to intervene in a system beyond its borders, but when an Imperial Navy task force finally arrived at Talos, the intruder immediately disappeared. Imperial and Sword Worlds vessels were both present, but could not follow the craft as it moved off under extremely high acceleration (10-12G). Since no jump signature was detected and an intense search of the inner system revealed nothing, it was concluded that the intruder had fled to the unsearchable vastness of the system’s Oort Cloud. There have been dozens of reported encounters with the strange vessel in the remote, sunless reaches of the Talos System over the past four centuries, but none of these has ever been confirmed.
The most widely accepted theory is that the intruder is an automated vessel that continues to mindlessly follow its ancient and inscrutable programming. The most fascinating and perplexing question, of course, is whether the craft was protecting the Talosians or imprisoning them on the planet, but other riddles abound. Whatever its purpose, why did the intruder disappear and then return five standard centuries later? Its flight from the Imperial Navy task force in 708 seems logical enough, but why has the intruder never returned to the inner system in the four centuries since? Last but not least, who or what built the vessel in the first place? Popular speculation on this last question inevitably points to the Ancients, whose homeworld has been tentatively placed in the neighboring Five Sisters subsector, but most reputable scholars reject this notion because human inhabitation of Talos is at most 2,500 standard years old.