“It is a sight to behold: like a giant spider web - dozens upon dozens of rope bridges and lines are strung between the hills of the district. And the people. They move along these slender swaying lines as if they were walking down a boulevard.”, The Journal of Mathius Redcap
A rumour of the knights of some powerful king that sleep until danger threatens the kingdom.
The truth is that they were rebels, trying to split the kingdom. Once captured they were put into an enchanted sleep, protected from age and harm, until their aims have been carried out by others in which case they will awaken.
There is a loophole in the spell in that trying to take one of their weapons will also awaken them.