Complex sentence: Michael II, called Psellus, "the stammerer," Byzantine emperor 820-829, was a native of Amorium in Phrygia, who began life as a private soldier, but rose by his talents to the rank of general.
Split into simpler sentences: Michael II, called Psellus, "the stammerer," or "the Amorian" (770-829) reigned as Byzantine emperor 820-829. Born in Amorium in Phrygia, he began his career as a private soldier, but rose by his talents to the rank of general.