Complex sentence: At 80 years old, the death of Sultan Jàqmaq allowed his son, Uthman (fathered from a Greek slave) to succeed to the title of Al-Malik al-Mansur Fakhr ad-Din Uthman.
Split into simpler sentences: At 80 years old, the death of Sultan Jàqmaq allowed his son to succeed the designated Uthman who was the son of a Greek slave. He succeeded to the title of al-Malik al-Mansur Fakhr ad-Din Uthman.