Official canonical events of original, based on revelations in the sequels.

[This doesn't include the period of nostagia/reboot/Jamie Lee Curtis-vanity-projects that we've been ever-so-thankfully (lol) graced with since 1998. No, I'm talking about the actual series here.]

An ancient druidic ritual of the occult was placed on young Michael Myers of Haddonfield, Illinois in 1963 by Dr. Wynn of Smith’s Grove & Ms. Blankenship, the woman living across the street where Michael is seen coming from in the opening shot of the original film.

On Halloween night, in conjunction with the positioning of a seasonal constellation, one child from each “tribe” will off his bloodline in sacrifice with the spirit of the Samhain festivities being demonstrated.

In return, the rest of the community receive good luck 🍀 and are spared the bad fortune of war, famine, disease and so forth.

Myers (or whoever else has been deemed the Thorn enforcer) seems to obtain telepathic abilities to aid in their pursuit of loved ones.

Also, the Wallace house, Annie, Lynda and Bob were proxies for Judith, his parents, and his own home. He did them first, you see, ceremonially, as substitutes. Then he came after his final 'real' sister, Laurie—as that's how the process should have all went for him in 1963. He is thwarted by his psychiatrist, Dr. Sam Loomis, the hero of the story.