Complex sentence: Pope Sabinian (d.22 February 606) was Pope from 13 September 604 to his death in 606, during the Byzantine (Eastern Roman) domination of the Papacy; he was the fourth former "apocrisiarius" to Constantinople be elected pope.
Split into simpler sentences: Pope Sabinian (d.22 February 606) was Pope from 13 September 604 to his death in 606. Pope during the Byzantine (Eastern Roman) domination of the Papacy, he was fourth former "apocrisiarius" to Constantinople elected pope.