Palace of Shadow

The Palace of Shadow is the final area that Mario and his comrades visit in Paper Mario: The Thousand-Year Door, where the Shadow Queen resides. It is found behind the Thousand-Year Door. The Palace is one fourth of the old city that was ruined 1000 years ago. Over the years that the Queen reined the Palace became rich with stolen treasure.

In this palace, the Shadow Queen possesses Peach, who Sir Grodus had delivered to her. Mario and co. drudged through the palace and its inhabitants, including the middle sibling in the "tail" family, Gloomtail. Mario and co. later fought with the Shadow Sirens, who now consisted of Beldam, Marilyn and Doopliss. Soon after, Mario and company finally made it to the Shadow Queen's lair, where Sir Grodus was. Mario and his party defeated him, and surprisingly King Bowser and Kammy Koopa, Sir Grodus retreats to a crypt to give Princess Peach as an offering to the Shadow Queen.

The first room is rich and very detailed with roses and patterns. Past this is a bridge across an expanse of water, the cave "ceiling" can be seen here. The room afterwards is a large staircase that goes even farther underground. Later, a garden area shows off some streams and the Riddle Tower. To get there walk through a hallway to Gloomtail to get the Star Key. After the tower is completed ancient machinery will activate, causing the hallway to collapse, revealing a large back area filled with enemies. One of the last rooms is a huge chamber with odd pillars, and then, the throne room where Grodus has Princess Peach. A secret door shows a huge staircase down to the crypt containing the Shadow Queen.

After Grodus awakens the evil Queen it possessed Peach. Grodus ordered the Queen to attack Mario, but ended up getting destroyed because of his own ego. The Shadow Sirens arrived and Beldam took full credit for the awakening of the queen. The Shadow Queen asked Mario and co. to be her eternal slaves, but Mario and company refused and engaged into battle with the Queen, but the Shadow Queen found Peach's body too weak and used her true form to destroy Mario and company. The Crystal Stars scattered throughout to where they were found and let everyone know Mario and his team were in trouble. Everyone sent their positive thoughts and wishes to Mario and his friends. Peach managed to break out of the evil Queen's control and replenished Mario and his team's HP, FP and Star Power. Mario and co. destroyed the Shadow Queen and released Peach from her control.

Trivia

 * The Shadow Queen's crypt is the farthest point in the Palace and game. With rough estimation, it is approximately 325 feet below Rougeport. That's not much horizontally, but vertically it's a very long drop.
 * According to the Magical Map the Palace may be somewhere near the middle of the ocean. However, it may be is because the Palace of Shadow dot in the map didn't fit on the land.
 * Many people call this place Palace of Shadows or The Shadow Palace.