Complex sentence: As an act of vengeance for being fooled as such he mutilated the work with his chisel, whereupon the Duke, considering himself affronted, denounced Torrigiano as a heretic.
Split into simpler sentences: As an act of vengeance for being fooled as such he mutilated the work with his chisel. Whereupon the Duke, considering himself affronted, denounced Torrigiano as a heretic.