After clearing the room of enemies (which notably should be stronger and harder to defeat by now), strike the door and synthesize using a card with a value of 1 or more. In Room 2, go to the north door and strike it. Use a card with a value of 1 or more. In Room 3 and Room 4, use the right door and you'll reach Room 5. Use an Attack Card, a card with a green border, and the Key of Beginnings.
Hades can be quite a challenge, but still shouldn't be all too bad. When he's blue, he'll usually either be floating around or using a close-range fire attack which shouldn't be too hard to break. After he's taken enough of a beating in this form, Hades will change color and start using attacks that deal more damage, including both short and long-range attacks. Try to get behind him as often as you can when he's in this form, and eventually he'll switch back to his initial form. Also try to get to Dark Mode before Hades can change form. Hades' attacks are as follows:
- This is one of his closer-ranged attacks. Hades points his finger and fire appears to attack Riku.
- Hades throws a large ball of fire. Despite its size, this attack is easily the easiest one of his to dodge.
- Hades switches to his angry self, allowing him to use more moves that deal more damage.
- A move in which Hades creates a wave of fire. This is the hardest move to avoid without breaking, and, as such, can only be used when he goes through his transformation.
After you defeat Hades, go back to Room 4 and then use the north door. In Room 6, use the north door again to reach Room 7. From Room 7, you can leave and return to Castle Oblivion.