The Beacon of Kahless was a ancient sacred Klingon artifact.
There are many stories which have been passed down from generation to generation regarding the legendary Klingon known as Kahless the Unforgettable.
There is a story that Kahless, prior to his departure, that he built a beacon, later called the Beacon of Kahless, which will, when lit, assemble the Houses to combat a great threat to the Klingon Empire.
This relic was sought by many over the centuries without avail. Very little was known about the beacon; not even what the beacon was expected to look like. Most adults consider this beacon to be a fable told for the amusement of children.
The Klingon Leader T'Kuvma, claimed to have found it. However in reality the Beacon that T'Kuvma found was actually a carving created by his loyal servant Khel in secret as the latter believed the Beacon itself was juts a myth and the true beacon was T'Kuvma himself.(DSC - The Light of Kahless comic: "Issue 4")