Complex sentence: Around this time, three swords--symbols of kingship since ancient times--were being used in the coronation ceremony to represent the king's powers in the administration of justice: the Sword of Spiritual Justice, Sword of Temporal Justice, and Sword of Mercy.
Split into simpler sentences: Around this time, swords--symbols of kingship since ancient times--were introduced into the coronation ceremony. Three swords were used to represent the king's powers in the administration of justice: the Sword of Spiritual Justice, Sword of Temporal Justice and Sword of Mercy.