The Hall of Collosia is a location in Antiqua. It is located far north of the Western Bank, and is the hiding place for one of the Diamond Eyes. The Hall is full of pitfalls; some require the player to hit switches with the Bronze Spear to extend a bridge, other pits have invisible platforms that can be revealed with Revealer.
The Hero came to the Hall seeking the Diamond Eyes. He was successful in his expedition.
Madronius' brother lives in a secret area in the Hall, and gives the Fireball formula. His chamber can be accessed by a hidden passage in the large chamber with the Mad Monk, in the south-west corner of the room.