“ 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.”
“ The village sits on the edge of the deep fjord, often engulfed in mist or rain. Its people are fishermen, who work even through the sea-ravaging winter. And they pray to the gods of the deep.
At the beginning of every winter they hold a summoning ceremony. Three boats are taken out into the fjord, a hornsman on each. The mournful horns are blown in the language of the whales, the gods of the deep. The whales sometimes appear in answer to these calls, and it is taken as a good omen when they do.
To a party of PCs wandering the misty hills and valleys nearby however, the doleful whalesong of the horns can be disturbing and misinterpreted...”
“ When you sleep, your soul briefly returns to the place where it was created/goes to when it dies, and seeks nourishment. Everybody's soul is created with a little link (or you could say a greater entity calls it back) to that place so that it can return easily, but upon death, the soul returns via that and annihilates the link as if returns.
Also, as an added thingy, you could say the entity supplying the link, or residue of the links themselves, (whichever) is the source of all arcane power.”