Wild Arms - Part 28: Leviathan (Optional Boss)

In order to fight the Leviathan that sunk the Sweet Candy, you must first get the Sweet Candy restored. If you've been rebuilding Adlehyde as you played, eventually there will be a familiar sailor that moves in and gives you the restored ship. From there, you just need to find the sucker in the ocean. It took me a long time to do so, and I've edited in the parts where I was talking about previous games.

The boss is fairly easy for this stage of the game, and your reward for sinking this golem is Cecilia's ultimate armor, the Pret-a-porte. I don't know why they chose that name as it means "ready to wear" as in the term used to describe clothes you can just buy off a store shelf. Probably something else lost in translation.