I thought it was Kraken at first too, but at the same time, I'd rather see Kraken alongside Lich, Marilith, and Tiamat rather than as a standalone boss. He's FFI's Elemental Archfiend of Water, for crying out loud! That'd be like having the final boss of a dungeon be Cagnazzo, but with Scarmiglione, Barbariccia, and Rubicante nowhere to be found.