Hogwarts Legacy is a massive game with much to do beyond the main story. Joining school as a 5th year, the player is given a Field Guide to help them catch up to the other 5th year. This Field Guide is a complete Hogwarts encyclopedia, but players must find all the missing pages scattered around the world to complete it.
One way to find these pages is by looking for blank mirrors around the world. Within the great hall is one of these mirrors, with a student attempting to figure out its secrets. Interacting with this student will have them request you figure it out and begins the quest Like A Moth To A Frame.
Beginning Like A Moth To A Frame
Beginning this quest is easy; as running through the hall, you'll hear a student pondering over the mirror. After interacting with the student, the quest will begin, and they will give you a hint as to how to complete it. This quest, and all butterfly mirrors in the world, react to the spell Lumos. Casting Lumos and getting closer to the mirror will have it reveal an image, with the image becoming more complete as your approach. Standing directly in front of the mirror while casting Lumos will display the full image, which is the location players must now find.
Completing The Quest
After seeing the mirror's location, you'll now need to find that location. Usually, these locations are not very far from the initial mirror, and in this case, reveals a statue. Facing the mirror, turn right and head back towards the large fountain in the center of the hall. Continue running past the fountain and down the stairs but don't exit through the door. At the door, turn left and head around the corner to reveal the statue, with a butterfly on the wall above it and to the left. Casting Revelio is also helpful as it will highlight the butterfly after the mirror's image has been revealed.
Now that you have discovered the butterfly approach it and cast Lumos again. While the spell is cast, and once you get close enough, the butterfly will fly towards your wand and fly around the light source. From here, it is important not to cast any other spells or do anything to make your sell cease its light source, as the spell canceling will have the butterfly return to its previous location on the wall.
While maintaining Lumos, head back the way you came and return to the mirror, with the butterfly following your light. Stand directly in front of the mirror and cease casting Lumos to see the butterfly return to its spot on the mirror. Stand as close to the mirror as possible before ceasing Lumos, as standing too far back may have the butterfly returning to its original location. After completing this mirror, tell your fellow student your discovery, and the quest is completed.