“ A certain type of toads, only found in the bleak swamps of Mournmist start falling on the city where the PC's are, like rain. Why?”
“ Since the local baron's wife died, to keep himself happy it is Christmas ( or the equivalent festival in your game world) every day in his castle.”
“ 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.”