The Crystal Stars are magic artifacts that appear in the game Paper Mario: The Thousand Year Door. Prior to the storyline, it is said that the Shadow Queen used the stars to spread her influence of power across the globe, as well as using them as resources for her power. After she was defeated by the original four heroes and sealed in the Palace of Shadow behind the Thousand-Year Door, the heroes used the crystal stars as keys for the door, which they scattered across the world. A magical map was created to divulge the locations of the stars.
During the final boss battle with the Shadow Queen, when Mario and Co. are helpless against the Queen's power, the Crystal Stars Mario had collected are sent out to all of Mario's friends and allies he had aquired throughout the game, who then send Mario their good thoughts and positive energy, which shatters the Shadow Queen's power, briefly relinquishing her control of Princess Peach, who heals Mario and Co. with the last of her power.