The Shadow Creatures are five ghost-like monsters that Ned encounters after eating tons of sugary foods and playing video games. They follow him into his room and sink into his bed and make Ned have nightmares. Each of the shadows rule a different Nightmare World. Though Ned does not see them or hear them in real life they are visible and can speak in the real world. They also can morph into different shapes as shadows. They represent someone or something in real life that Ned knows about. In each nightmare, Ned must complete an objective to reveal a piece of a shadow, revealing a bit more about who the Shadow represents. Each shadow has three parts, the lower half, the upper half and finally the head. After Ned uncovers the shadows identity, the Nightmare World that the shadow once ruled is completed. Once all five shadows and thier Nightmare World has been defeated, Ned will return to The Quilt, where he will see all the people or objects that were once the shadows haunting Ned.
The Graveyard Shadow is apparenty the man-in-charge though he is pushed around by the Medical Shadow. The School Shadow and Bathroom Shadow fight on occasion and strangely Attic, Basement and Beyond Shadow never talks with the other shadows.