- A secret training space beneath the training hall. Used only for the special sword techniques. Gustav decides who may enter.
- Twin Blade Gustav (Boss Battle)
- Medal: 3000 points/2400 silver/1800 bronze
- Time: 10 minutes
- Times Damage Bonus: 1000
- Get: Hurricane Spin move (when win)
- Exits: Underground Training Hall Space 10 (down)
- Equip weapons in both hands (x and y), alternate repeatedly hitting him when he is not using his hurricane move. When he uses his hurricane move then run out of his way diagonally. Once you beat him and get his Hurricane Spin move then you can use it on him to get a gold score.
- No exploration (but boss battle takes place here)
- There is a Big Key door in the Training Hall main room that leads to Underground Training Hall Space 11 and Underground Training Hall Space 12. To get the Big Key you will have to beat the boss of the Site of Cyril dungeon (Torsol) in Samiad and meet Witch Ellie in the Witch's Desert Palace Prison. (When exit Guardian's Domain then you will get a cutscene where you are thrown into Prison)