Memoria (Final Fantasy IX)

Memoria is the final dungeon in Final Fantasy IX.

Story
After the destruction of Terra at the hands of Kuja, it appeared above the Iifa Tree. It is made from the memories of Zidane and his friends. The four Chaos guardians, Maliris, Tiamat, Kraken and Lich fight the party once more here. However, not only is the memories of Zidane's party here, but the very memories of Gaia itself. Throughout all of Memoria, various bits of history in Gaia's past are examined. Including the time when the planet was covered in water, to present events like the incidents in Alexandria. Throughout the Dungeon, Garland's voice can be heard, guiding the Party to their destination. The secret boss Hades can be fought here, who is the Master Synthesist referred to in one of Mogster's early lectures. He can synth two pumice pieces to create the Pumice that can be used to summon the Eidolon Ark.

Since the Iifa tree and Necron have many things in common with the Void from Final Fantasy V, they may be part of it. Indeed, if you are quick enough to get Excalibur II, there is a note that seems to have been left for Gilgamesh. The note says:

"To Brother Gil - Bro, I found the sword, like you told me. But there were two. One of 'em had a lame name, Something II. It was a dingy, old thing with flashy decorations, something you'd probably like. So I went with Excalipur. I'll be back after I find the Tin Armor." —Enkido

Gilgamesh is one of the few people to survive the void. This is reinforced by the fact that he can be found outside in Gaia, as Alleyway Jack, the man who attempts to mug Dagger in Treno, and the Treasure Hunter in Daguerro. He also appears in many of the other Final Fantasy titles.