The Tkon Empire was a massive empire that existed over 600,000 years ago. The Empire had a population of trillions and was incredibly advanced technologically. The Tkon had the ability to move entire star systems, using planets as outposts for defense. Their empire collapsed not long after the Age of Makto, when the central star of their home system went supernova.
The Empire employed guardians known as portals to defend its outposts and to act as gatekeepers for those seeking entry to the Empire. At least one such guardian, Portal 63, survived and was encountered by the Federation starship USS Enterprise-D on a planet in the Delphi Ardu system in 2364. This occasion was the first instance of contact with the extinct Tkon.
Beyond some information regarding planets in the Empire and an understanding of their script and some of their history, little is known of the Tkon by the Federation. Even students of archeology such as Jean-Luc Picard had limited knowledge in the 24th century. (TNG: "The Last Outpost")
Background information Edit
The writers of the episode "To the Death" mistakenly referred to the Iconians as the Tkon, causing the art department to design and produce sets based on graphics seen in "The Last Outpost". The error was discovered not long before shooting took place and corrected. (Star Trek: Deep Space Nine Companion, pp. 348-349)
In the Star Trek: The Next Generation - Q Continuum novels, Q reveals the history of the Tkon Empire's final days with Captain Picard while explaining Q's history with the malevolent entity 0. After Q allowed 0 and his allies access to this universe, he selected the Tkon Empire as a lesser species for 0 and his allies to 'test', with their actions provoking a civil war between the central Tkon homeworld and its outer colonies over the costs of the 'Great Endeavour', a plan to save their homeworld from its dying sun. Despite fifty years of conflict, the Tkon Empire not only survives but completes the Great Endeavour on schedule, intending to use an elaborate transporter array to teleport their sun completely out of their solar system and simultaneously replace it with a new, fresh one before their system could suffer from its loss. However, 0 triggers the collapse of their sun ahead of schedule in a fit of pique at the Tkon 'winning' his 'game', the elder Q noting to Picard that he at least adheres to his rules in his tests of Picard where 0 changed the rules the moment he was about to lose. This action resulted in 0's banishment from the galaxy by the Q Continuum, as well as the creation of the galactic barrier to prevent him ever returning. Q notes to Picard that the transporter array the Tkon were going to use to move the fresh star still exists in the present, recommending that Picard salvage it once he returns to his own time before someone else does.