The Belfry clock is a room from Luigi's Mansion 2 in the Old Clockworks; it's also where the final mission of the mansion mainly takes place, with Luigi fighting the Overset Possessor who possessed the giant clock and is trying summon ghosts to help him attack Luigi to prevent him from getting a piece of the Dark Moon. Luigi keeps fighting ghosts due to the possessor summoning them.
The belfry clock appears as a giant clock on top of the tower. It also had a coo coo bird. When the overset possessor reverse the clock hands, the number on the clock disappears. Luigi had to replace the numbers by defeating all ghosts in an hour, with a total of 12 hours. Every 4 hours, Luigi and the overset Possessor will face off in a one-on-one brawl down in the clock