After the events of the Final Battle of No Way Home, things start to go awry. Where instead of things wrapping up as intended, a new unexpected threat breaks into the main universe. This threat being the sinister Christmastime demon, "Mariah". Now, Peter's 1,2 and 3, along with Doctor Strange, have to kill her, before she can affect the very nature of their reality. Causing everyone to be forced to listen to her song for all eternity.—Zack Walker