Complex sentence: Tyrannus manages to rescue Piso, but returns to a fatally wounded Caesar; however, Caesar remains alive long enough to tell him that Octavius is his chosen successor and orders Tyrannus to protect him.
Split into simpler sentences: Tyrannus manages to rescue Piso, but returns to a fatally wounded Caesar. However, Caesar remains alive long enough to tell him that Octavius is his chosen successor and orders Tyrannus to protect him.