Long since the days that Camelot stood as a tall and mighty kingdom. But it still stands. It has withheld the test of time as a school; Hogwarts. Now the Old Religion summons Merlin back. During the time of the 'Golden Trio' the reincarnated residents of Camelot have made a new appearance. All must join together to survive and stop the Dark Lord and newly resurrected Morgana Le Fey

Winter is necessary. So is fun. So by extension, Jack Frost is a necessity. Fear is needed to keep the world alive. The Boogeyman is needed. (AKA where the heck is the "explanation" genre?)