Hogwarts was struck with a sickness so deadly so great of a killer that even Dumbledore trembled at it's very name even the beasts that reside around the castle haven't set foot in areas with signs of the decease the disease was called dementor
so Dumbledore thought to lock himself,the creatures that are willing to follow his orders and his friend as well as his students. Since the castle is so large it has 7 rooms each room has it's own color
the colors are scarlet,blue,green,yellow,gold,bronze and black with the black room having a clock in it every time the clock strikes 12 they'd stop and listen to the chimes from the clock
all the rooms where filled with masqueraders who were matching the rooms colors,every time the black clock struck the party goers would stop and and listen to the clocks chime even after the clock struck 12 many noticed there was a masquerader who has never been seen before.
the party goes where flabbergasted at the sight of the unknown party goer,soon a feeling of fear and disgust could be felt from the unknown party goer then the dancers soon crowded around him but none dared to touch it next the party ran towards the black room.
dumbledore chased after the masquerader only to realize that it was a dementor then it was too late he was already dead soon the music stopped and all the rooms slowly became empty as everybody began to die,once the clock struck 12 one last time not a single person was standing but only the demontor