Amaranthine - A Death Solar: Book One, Volume One by Ben Longoria

Following a cataclysmic civil war between the colonists of Mars and a corrupt Earth a new empire has emerged from the ashes of nuclear war. Lead by history’s only known immortal, a man named Avernus, the nation of the Triad forces its way across the black of space conquering worlds in the name of God. The holy crusade has lasted thousands of years and thousands of worlds have been won through diplomacy or war. Throughout all the years Avernus has remained a constant guide for his people. Through him the Lord’s will is carried out. But serving a distant master is exhausting and despite all his powers Avernus is still a man. Yet, something has changed. On the horizon lies the end of the quest where Avernus will face an enemy who knows his long tattered past and has abilities that surpass his own.