Exdeath's sealed cave is an unnamed and unvisitable location in Final Fantasy V. It is located in a x-shaped forest on northwest part of the eastern continent in Bartz's world. According to the Warriors of Dawn, the location was chosen to seal the evil warlock due to being the place where the power of the four crystals gathered.
During the events of Final Fantasy V, the Sealed Castle of Kuza appeared in the cave where Exdeath had been sealed.
Thirty years before the events of Final Fantasy V, the Dawn Warriors—Galuf Halm Baldesion, Dorgann Klauser, Kelger Vlondett, and Xezat Matias Surgate—followed Exdeath from their world to the other half of Planet R that was separated to seal the Void. As the warriors were unable to defeat Exdeath, they chose to harness the power of the four crystals of this world to seal the evil warlock within the cave. Feeling responsible, and fearing that Exdeath might one day break free of the seal, Dorgann remained behind in this world to guard the seal, while his friends returned to their original world.
The seal remained unbroken for 30 years, but its power slowly weakened (in part due to the kingdoms having been harnessing the powers of the wind, fire, and water crystals using amplification devices). Sensing opportunity, Exdeath took control of various important individuals and monsters to speed up the process, leading to the destruction of the four crystals, freeing him from imprisonment.