What are the chorus characters in Macbeth?

If you are referring to "chorus characters" as characters
who act as a unified whole (similar to the role of the chorus in Greek plays) then the
three witches would be the chorus characters in Macbeth.  The three
act in unison when giving Macbeth and Banquo the predictions for their future.  They
also continue to plot future events.  When Hecate enters the play, she is angry with all
three witches for conspiring together and telling Macbeth information that he should not
know.  Throughout the play, the witches serve as a force for challenging Macbeth's sense
of morality and righteousness.  So, they serve a similar role in
Macbeth as the chorus does in Greek plays.