The beautiful Fairy Castle of Princess Callia, favored daughter of deranged Emperor Sentatian.
It is a box of fairly standard children’s toys. There are dolls, blocks, carved knights and animals. Everyone will think, “Oh I had one of those when I was young.”
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.