Complex sentence: However, Sauron always remained faithful in his allegiance to Melkor; as Sauron expanded his empire into new lands, with it he would also spread a cult devoted to Melkor-worship, promising that one day he would return from the Void.
Split into simpler sentences: However, Sauron always remained faithful in his allegiance to Melkor. As Sauron expanded his empire into new lands, with it he would also spread a cult devoted to Melkor-worship, promising that one day he would return from the Void.