The Crystal Palace (月の民の館, Tsuki no Tami no Yakata?, lit. Mansion of the Moon People), also known as Lunar's Lair, is a location in Final Fantasy IV and Final Fantasy IV: The After Years. It is where Fusoya guards the Lunarians in their Lunar Sleep. It is also where the eight Lunar Crystals are enshrined. It also contains recovery points.
Cecil, Rydia, Rosa, and Edge arrive here and meet Fusoya, who has apparently been expecting them. Fusoya tells Cecil and his friends the truth about Kluya, Zemus, Golbez, and the Crystals. He then agrees to accompany them to defeat the Giant of Babil.
Golbez and Fusoya leave the Crystal Palace to inspect the Impact Crater. They later return to the palace, where the Mysterious Girl appears and attacks them with Leviathan. They find the Crystals of the Moon darkened, and the Crystals shatter one by one as the two head into the Subterrane to check on the Lunarians. As the final Crystal shatters, Zeromus's Malice is released and attacks them.
It is the first room from the entrance, and it is where Fusoya, who is sitting on the crystal dais, is found. Fusoya tells the party about Cecil's origins and about the Giant's impending danger. On the opposite sides of the room, two cure pots (HP and status is on the left, MP is one the right) are available for use.
It is the room after 1F, and is accessible only after the events of the Giant of Babil. 2F holds all of the Red Moon's crystals, and when prompted, inform the player of Zemus. At the center of the room is the teleporter that will warp the party to the Red Moon's core.
The background music that plays inside the Crystal Palace is the "Prelude".