Complex sentence: Towards the end of 221, Elagabalus ended his marriage to Annia Aurelia Faustina and divorced her; however, it is unknown why Elagabalus ended his marriage to Annia Aurelia Faustina.
Split into simpler sentences: Towards the end of 221, Elagabalus ended his marriage to Annia Aurelia Faustina and divorced her. However, it is unknown why Elagabalus ended his marriage to Annia Aurelia Faustina.