Note: White Boa required

To the north of the main continent is a small inlet that is blocked by ice. Break the ice using the White Boa, then launch the Nautilus. Dive and you'll find the entrance to the Forgotten Cave. Loot the items in the area and fight a secret boss in the upper level.

Seth will be a fixed character here. Equip your attackers with Bio-Killer rings. This enemy can deal massive damage by attacking characters consecutively. Make sure to cast All-Generatus and other support spells to everybody and attack buffs to your attackers. Forceus works great, while having Perfect hits against the enemy further increases your damage potential. With just HP10000, this battle shouldnt take that long.

After the battle youll receive Gravity Rave (Seth only) and Gravity Ring. You will also receive Aneiras Plume and unlock the corresponding achievement for defeating this boss. Now time to get the remaining items. Jump to the west side to get (x6) Forbidden Explosives. Head north from the main area to reach a small deadend with a chest containing (x6) Ruin Masks. You may not leave the cave and head to the Numara Atoll.