The hall of costumes is near the crypt of past Phantoms and were all the past Phantoms costumes are kept and belongings.

It started out as a simple wooden cupboard and then the 21st Phantom has outfitted a modification of the room with past costumes on dummies and past weapons in display cabinets. Presents like a museum exhibition.

At least in the old room, the room used to hold past Phantom costumes. Unsure if these have been included in the new outfitted room.