A fey spirit masks itself as a bee which investigates all who travel within a specific section of the forest. Any the bee finds worthy are allowed to see the hidden opening into the fey kingdom, just off of the trail. Any deemed unworthy see only the bee, buzzing around around them momentarily before moving on.
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.