Complex sentence: The embassy was led by a Genoese in the service of the Mongol emperor, Andrea di Nascio, and accompanied by another Genoese, Andalò di Savignone.
Split into simpler sentences: The embassy was led by a Genoese, Andrea di Nascio, in the service of the Mongol emperor. He was also accompanied by another Genoese, Andalò di Savignone.