There are numerous synonyms for the phrase "hold the reins of empire" that can be used to convey the same meaning. Some of these synonyms include leading the empire, governing the empire, controlling the empire, managing the empire, ruling the empire, steering the empire, commanding the empire, and piloting the empire. All of these phrases indicate that someone is in charge of directing the operations of an empire, making decisions that impact the lives of its people, and shaping its destiny. Whether you prefer one of these synonyms or the original phrase, they all emphasize the importance of leadership and the responsibility that comes with it.