100 Sleeping Princes and the Kingdom of Dreams

A normal girl is transported to another world, known as the Dream World. Here, dreams are the energy of all beings living within it. The protagonist is revealed to be the long-lost Princess of Traumere and therefore the princess of the Dream World, and she must defend the world from creatures known as Dream Eaters, who steal people's dreams. Using a special ring, she must rescue the various princes of the world, trapped in eternal slumber within their own rings, and team up with them to save the Dream World.