Star Trek: Serenity
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.
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.