An ancient and immensely powerful civilisation, numbering in the trillions and able to move stars, that was wiped out when its sun went supernova some six hundred thousand years before the 24th century.
The Tkon Empire is discovered in the Next Generation episode The Last Outpost. In 2364 the Enterprise-D pursues a Ferengi ship to Delphi Ardu IV, where both vessels are seized and drained by a force from the planet, which Data identifies as a remote outpost of the long-dead Tkon.
Tkon history was reckoned in ages, among them Bastu, Cimi, Xora and Makto, and the empire fell during the Age of Makto. On the surface the away team wakes the outpost's guardian, Portal 63, who believes the empire still stands and prepares to judge the intruders.
The Ferengi accuse the humans of barbarism. Portal instead tests Riker, who answers with the philosophy of Sun Tzu and is found worthy. Told that his empire is gone, the guardian releases both ships and returns to sleep. The episode is also the first on-screen appearance of the Ferengi.