Warhammer: After Sleeping for Thousands of Years, the Emperor's Brother Returns

The most powerful psyker in the world, brother of the Emperor, fought alongside him to build the Empire of Mankind across the galaxy. But he fell asleep after the Horus Heresy, and when he woke up ten thousand years later, he found that his home had been stolen! The rational civilization I built with my own hands has actually been corrupted into a dark kingdom of gods worshiping false gods? Good! Very good! Since you have ruined the empire, I will rebuild it with my own hands!