In Hogwarts Legacy, the Great Hall is one of the six areas of the Hogwarts School of Witchcraft and Wizardry. It overlooks the lake on the southwest side of the school, and has three Floo Flames: one at the boathouse on the lake, one in the Great Hall itself, and one in the Viaduct Courtyard. The Great Hall is also the location of one of the school’s arithmancy doors, which must be unlocked using the ancient magical art of arithmancy (which is math magic, basically). These door puzzles can be confusing at first, but with a little help you can make the solutions add up.
Related: All Demiguise Statue locations in Hogwarts in Hogwarts Legacy
How to open the puzzle door in the Great Hall in Hogwarts Legacy
Screenshot by Gamepur
The Great Hall puzzle door is at the end of a corridor leading off the northeast corner of the Great Hall itself. Head east from the Great Hall Floo Flame, then turn left. The “?” and “??” triangles are also in this same corridor.
Screenshot by Gamepur
To unlock the door, you have to roll the triangles so that they display the creature icon that represents the number that will make the points of the triangles add up to the numbers in the middle of the triangles. The creature icons are numbered 0 to 9, from left to right, so the demiguide is 0 and the snakes are 9. The top triangle reads snakes (9) + 7 + ? = 24. This means the “?” must be 8, which is represented by the spider icon, so roll the “?” triangle until it displays a spider.
Screenshot by Gamepur
The bottom triangle reads 11 + demiguise (0) + ?? = 14. This means that the “??” must be 3, which is represented by the hydra, so roll the “??” triangle until it displays a hydra. Now you can open the door and loot the chests inside, one of which contains the Crests Conjuration exploration collectible.
