Character ‘King Duncan’ is found in Shakespeare's play -

Character ‘King Duncan' is found in Shakespeare's tragedy Macbeth.
Macbeth, tragedy in five acts by William Shakespeare.

Its important characters are
- Macbeth,
- Lady Macbeth,
- Duncan,
- Banquo,
- Three Witches.
Macbeth and Banquo are generals serving King Duncan of Scotland.

Source: Britannica.com