Castle Burtgang (ブルトガング城, Burutogangu Jō?) is a location in Final Fantasy Dimensions located to the north of Burtgang. The royal Burtgang family used to live here but almost all of them were killed, Sarah being the only survivor.
Sarah, who left Berth alone to find Gawain, is ambushed by imperial soldiers when she enters Castle Burtgang and is saved by Gawain. Meanwhile, the other Warriors of Light emerge from the Underwater Cave and meet Sarah and Gawain, deciding to take the castle from the Avalon Empire.
Entering the throne room, they meet a woman who resembles Sarah's mother. She lures Sarah to go with her. While Gawain is happy to meet the queen, Sarah knows her parents were killed long ago. Styx reveals her true form and attacks the party, but is defeated.
Shango appears and asks Styx to accepts her defeat honorably, striking her with lightning. Gawain gives Sarah his sword, tells Sol to protect Sarah, and urges them to leave despite Sarah's order. Gawain single-handedly challenges Shango but is defeated.
The others head to the castle gate and assume the surrounding area is full of soldiers. A battleship emerges from the sea, turns into an airship and flies to Castle Burtgang. It turns out to be Dr. Lugae's battleship. It picks up the warriors and flies away. Gawain's sword glows and gives the warriors its power. Dusk contacts somebody, and the team heads to Mysidia.
When in the last part of Chapter 4 (World of Nil/The Void), the party must fight a boss to restore Castle Burtgang. When coming back from the boss, the party must talk to the ghost of the King of Burtgang sitting in the throne room twice to activate the cutscene that will convert Galantine to Excalibur. If the party leaves the room without doing this, the castle's ghosts disappear and the party can never get the Excalibur.