It's never an actual "magic" thing like say the Ark of the Covenant was in Indiana Jones. It's always some
virus, the properties of a plant or something causing hallucinations.
You're thinking of something else, I guess. In 1 it was
cursed gold
, it 2 it was
the tree of life
, and in 3 it was
literal genies
. If I ever get around to 4, I'll report back.