Complex sentence: Thus Aegon I Targaryen, now known as Aegon the Conqueror, took control of the Seven Kingdoms except Dorne, left unconquered and acknowledged as a sovereign state under the rule of the Martells of Sunspear.
Split into simpler sentences: Thus Aegon I Targaryen, now known as Aegon the Conqueror, took control of the Seven Kingdoms. At this time Dorne was left unconquered and acknowledged as a sovereign state under the rule of the Martells of Sunspear.