The Qualm is a giant mass of tentacles and leaves with hundreds of mouth-like pods lined with teeth. It is about 1/8 of the size of Earth's moon, and it travels through space looking for nutrient rich planets that it can suck dry.
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.