Warhammer: After Ten Thousand Years of Slumber, the Emperor's Brother Returns

The strongest Psyker in the world, the Emperor's brother, fought at his side and helped build a human empire spanning the galaxy. But he fell into a deep sleep after the Horus Heresy. When he awoke ten thousand years later, he discovered his home had been stolen! The rational civilization I built with my own hands had been corrupted into a dark theocracy devoted to false gods? Good! Very good! If you've ruined the Imperium, then I'll rebuild it with my own hands!