The Battle on Xezat's Fleet takes place when Xezat Matias Surgate and his army attack the southeastern shore near Castle Exdeath. When Galuf Halm Baldesion and the rest of the Warriors of Light join the battle, Exdeath's army attacks the fleet with Gilgamesh as commander.
The main battle is fought by Surgate forces, and the player only faces the monsters that attack Xezat's battleship, Gilgamesh included, while the rest of the army fights Exdeath's forces. Gilgamesh engages the Light Warriors with Enkidu who is killed and Gilgamesh escapes by swimming. The Warriors of Light join Xezat and head for an undercover attack on the southeastern Barrier Tower via underwater tunnels dug by Xezat's forces. He and the Warriors of Light split to destroy the devices that support the barrier.
Xezat shuts down the generator in the basement while the Light Warriors scale the tower. At the top they fight Atomos and destroy the barrier antenna. Xezat is trapped in the generator room by a monster as it explodes while the Light Warriors escape from the tower's collapse on the wind drake.
The battle ends with the destruction of the southeastern Barrier Tower that supports the shield enveloping Castle Exdeath, shutting down the barrier and rendering Castle Exdeath vulnerable. Although the Surgate forces are victorious, Xezat is killed in the destruction of the tower.