Who are the kings who bear "twofold balls & treble scepters"? [4.1.121]. Whom is Shakespeare referring to?
The "show of eight kings" is the fourth apparition that appears to Macbeth. These kings are all descendants of Banquo; just as the witches had originally predicted, his sons will become kings. In the procession of kings, the eighth carries a "glass," or mirror, turned toward the line in front of him, suggesting that the line is virtually infinite. Following the line, the bloody ghost of Banquo appears, pointing to the kings as his offspring. Macbeth's worst fears are confirmed. His plan to thwart the witches' prophecy failed.