The Demons were an ancient race of creatures that appear as the tertiary antagonists in the 2002 movie Scooby-Doo. They inhabited the island that would become the theme park Spooky Island.
They came under the control of Scrappy-Doo who in turn impersonated Emile Mondavarious through the Daemon Ritus, who sought to use the creatures to get revenge on Mystery Incorporated and conquer the world. The Demons disintegrated when exposed to sunlight, and thus used human bodies for protection.
The Demons once populated the lands which would become Spooky Island hundreds of years later.
Corrupted by the power of a pyramid-shaped artifact known as the Daemon Ritus, Scrappy-Doo took control of the Demons to complete their ancient ceremony and to conquer the world. He created a mechanical version of Spooky Island's creator and owner, and arranged for Mystery Inc. to be brought there.
However, Mystery Inc. discovered the Demons' weakness, and used a skeleton head disco ball to reflect sunlight, destroying the Demons. Scrappy was defeated shortly after.