The Thousand Year Door is an ancient doorway in the ruins and sewers under Rogueport in Paper Mario: The Thousand Year Door. It is the central focus for the story in the game as Mario and party must collect the Crystal Stars to open it to find where the princess may be, and the legendary treasure. Inside The Thousand Year Door is the Palace of Shadow where the legendary treasure sleeps that caused the cataclysm. The legendary treasure is a demon by the name of the Shadow Queen. She is the final boss who posses Princess Peach.