Sandman

In European folk-tradition (can anyone be more specific?), the sandman is the supernatural being who puts dreams in people's heads.

The Sandman title was taken for a mid-century crime-fighting comic book series by DC Comics, before being transformed by Neil Gaiman's reimagining of it as a supernatural and philosophical tale for DC's Vertigo line. His version is the story of one of the endless Dream (Others being Destruction, Desire, Dispair, Delirium, Death, Destiny) being imprisoned and then freed 40 years later.