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Geryon is an exclusive Superboss in the Nintendo DS remake of Final Fantasy IV in New Game+ mode . He is known as the "Malice of the Four Fiends" and can only be battled on a second or third playthrough of the game. He can be found within the Giant of Babil after the defeat of the four Archfiends, or on Mount Ordeals after the Giant of Babil becomes inaccessible.
Geryon is armed with all of the special attacks used by the Elemental Archfiends. These include Scarmiglione's Gas, Cagnazzo's Tsunami, Barbariccia's Maelstrom and Lightning, and Rubicante's Inferno. It is also able to use Curse, Stone Touch, and an incredibly powerful physical attack.
An effective way to defeat this boss is to be in the above levels, equip all characters with Adamant Armor, and to also equip Cursed Rings to turn the resistance of the elemental moves into absorption. This will render most of Geryon's attacks useless.
Geryon is the name of a demon in Dante's Divine Comedy. Its naming follows the trend of christening the Four Fiends after demons depicted on the poem.