Halloween: Everything You Need To Know About Michael Myers

According to the original novelized version of the first film and some vague whispers of dialogue that were added in the extended TV addition of the film, in the original timeline, Michael's powers stemmed from him being possessed by a Celtic spirit.

As detailed in the novel, this possession led to Michael hearing 'voices' in his head, telling him to kill. The novel even goes on to mention Samhain by name when ruminating on what could have caused the killings to occur on Halloween, a concept that wouldn't be incorporated into the film mythology until a full three years later in Halloween II.

The idea that it a Celtic spirit that possessed Michael also fits squarely within Carpenter's wheelhouse. Celtic folklore is where Samhain stems from and was also the basis for pretty much all of the story of Halloween III: Season of the Witch, the final Halloween film that Carpenter had any involvement with until the new film this year.

This also lends addition credence to why Michael was referred to as 'The Shape' in the original Halloween script, as it was a term used by New England Puritan minister Cotton Mather during the Salem Witch Trials to refer to the evil spirit which possessed the women.