Soul of Chaos
From Final Fantasy Wiki
Soul of Chaos is the collective name of the four bonus dungeons originating in the Dawn of Souls version of the original Final Fantasy, and reappearing in the 20th Anniversary Edition.
Their names are:
Each dungeon is tied to one of the four worldly elements (Earth, Fire, Water, and Wind respectively), and they are initially sealed by a statue of their element's respective Chaos Fiend (Lich for Earth, Marilith for Fire, Kraken for Water, and Tiamat for Wind). Once a Chaos Fiend is defeated and the elemental Crystal is restored, their statue will disappear, opening the way to the dungeon.
Each dungeon, with the exception of Earthgift Shrine, is significantly longer than any in the main game: Earthgift Shrine has 5 floors, Hellfire Chasm has 10, Lifespring Grotto has 20, and Whisperwind Cove has 40 floors. Every tenth floor has an exit portal to the World Map and a number of bosses available to battle, all major bosses from future games in the series: Earthgift Shrine features the Dark Crystal guardians from Final Fantasy III, Hellfire Chasm features the Archfiends from Final Fantasy IV, Lifespring Grotto features the famous Shinryu and Omega, Atomos and the recurring Gilgamesh from Final Fantasy V, and Whisperwind Cove features four of the more notorious bosses from Final Fantasy VI. The caves also include many new and powerful pieces of equipment that were not in the original game.
