What is the purpose of Hecate's interview with the other witches in Macbeth?
In Act III, Scene 5, the three witches are surprised to encounter Hecate at their haunt. The "patron" goddess of witches, often referred to as the "Mother," is extremely angered that the three sisters have had the effrontery to "trade and traffic with Macbeth" without having first consulted her, who is the power, "the mistress" of all their skills and abilities.
Added to this insult, Hecate informs the three witches that Macbeth is but a self-centered man
Hath been but for a wayward son,
Spiteful and wrathful: who, as others do,
Loves for his own ends, not for you. (3.5.11-13)
and undeserving of favors because he cares not for them. Further, she instructs the witches that she will use the night to create magic that will change Macbeth's fortune as he will become arrogant and become incautious. As she leaves the witches, she says she
Shall raise such artificial sprites
As by the strength of their illusion
Shall draw him on to his confusion.
He shall spurn fate, scorn death, and bear
His hopes ’bove wisdom, grace, and fear. (3.5.27-31)
Before she departs, Hecate reminds the witches that overconfidence is "mortals' chiefest enemy." This final statement, then, foreshadows the fated hubris of Macbeth and the errors he will commit.