Crystal Stars

The Crystal Stars are the seven stars Mario and his partners collect in Paper Mario: The Thousand-Year Door, and are the game's objectives. Upon collecting one, it will teach Mario a Special Move. When all seven are collected and shown at the pedestal in Rogueport Sewers, they will open the Thousand-Year Door to the Palace of Shadow.

The stars were created by the Shadow Queen to hold the essence of the heavens, and were placed in several locations to further expand her power. One of the castles built to hold the stars is Hooktail Castle. However, four heroes collected them and used their power against the Shadow Queen, but the heroes were cursed before the fight finished, and they couldn't let go of the Crystal Stars or else they will be trapped in a black chest. Knowing this, the heroes gave the Crystal Stars to others to protect.

The Crystal Stars consist of the Diamond Star, the Emerald Star, the Gold Star, the Ruby Star, the Sapphire Star, the Garnet Star, and the Crystal Star:
 * The Diamond Star was given to a healer the Toad hero met and was told to hide it in a place no one would look. Eventually, Hooktail got a hold of the star and kept it hidden in Hooktail Castle until Mario defeated her.
 * The Emerald Star was given to the Punies to protect, which they happily obliged to do after the Goomba hero saved them from monsters by hollowing out The Great Tree. During the course of Mario's adventure, Lord Crump steals the Emerald Star and Mario has to fight him in Magnus von Grapple to get it back.
 * The Gold Star is obtained in Glitzville, with its location kept secret by Grubba, whom Mario has to fight to obtain it. A fake Gold Star is placed on the Champ's Belt, which is given to the top ranked fighter of the Glitz Pit.
 * The Ruby Star was hidden in Creepy Steeple by the Boo hero. Doopliss later finds and keeps the Ruby Star until Mario defeats him.
 * The Sapphire Star was intended to remain hidden on Keelhaul Key by the Koopa hero, but the pirate Cortez stole it easily. After "defeating" Cortez in battle, he gives the Sapphire Star to Mario.
 * The Garnet Star is kept hidden in Poshley Sanctum, guarded by Pennington in a secret room even he did not know existed. A fake Garnet Star is on display for tourists.
 * The Crystal Star was originally kept hidden in Rogueport. However, Grodus and the X-Nauts found it and took it to their fortress on the Moon, where Mario battles Magnus von Grapple 2.0 to recover it.

The Crystal Stars also look similar to and have the same role as the Seven Stars in Super Mario RPG: Legend of the Seven Stars.