Complex sentence: Mauretania gave the empire one emperor, the equestrian Macrinus, who seized power after the assassination of Caracalla in 217 but was himself defeated and executed by Elagabalus the next year.
Split into simpler sentences: Mauretania gave the empire one emperor, the equestrian Macrinus. He seized power after the assassination of Caracalla in 217, but was himself defeated and executed by Elagabalus the next year.