Complex sentence: The dynasty, a bastion of Judaic and later of Ethiopian Orthodox Christianity, came to rule Ethiopia in the 10th Century A.D. Precise records of the dynasty's history had been maintained by the Ethiopian Orthodox monasteries to near antiquity.
Split into simpler sentences: The dynasty, a bastion first of Judaic and later of Ethiopian Orthodox Christianity, came to rule Ethiopia in the 10th Century AD. The descent and the records had been maintained by the Ethiopian Orthodox monasteries of near antiquity.