Hide And Seek Magnus -

: Appears toward the end of the episode to assist Jon, using a supernatural book to temporarily trap the NotThem. Other "Magnus" Hide and Seek References

: The protagonist, Head Archivist Jonathan Sims, is in a state of paranoia and has fled into the tunnels beneath the Magnus Institute. He believes a creature known as the "NotThem" —which has already replaced his assistant, Sasha James—is hunting him. Hide And Seek Magnus

This episode is a central piece of the show's overarching narrative, focusing on the horror of being replaced and the fear of the unknown. : Appears toward the end of the episode

: The hider who is actively replacing someone's life. Head Archivist Jonathan Sims