After this, you can talk to Chiko and head back to Thirdborn to finish the quest. What Should You Do With The Leviathan Heart As you return to Thirdborn, you'll have quite a few choices as to what ...

This fiery location is home to creatures such as the Secret rarity Magma Leviathan. After disembarking from your submarine, head deeper into the cave system. The Magma Leviathan is a special fish ...

The Frozen Leviathan is a Secret rarity fish that belongs to the Challenger's Deep Bestiary. Since it is exclusive to this layer of the Mariana Veil, you must head down to start your hunt.