the witches mischeif transcends into a killing game, their shear amusement of a plan unfolding, driving them to test Macbeth to the very limits of his sanity. They set up a circumstance of which they turn his noble friend, and "brother" the thane of fife, into a threat of his fruitless crown later on. They pray upon his insecurity of guilt and meaning, as they previously did with his ambition, the sense of an unnatural understanding of his psyche is unsettling. SO unnatural. yet another triumph at their foretelling, as banquo is later assassinated.