The Guests at the gate

The Gardeners gave humanity thirty months. Thirty months to hand over the entity living inside the Emperor, or watch the solar system stripped to its components.
What followed: forty-two crystal nodes deployed across inhabited space, a siege of the Mercury mines, a sixty-ship fleet against a thousand alien dodecahedra, and a man in a cave in the Himalayas channeling the faith of a billion pilgrims as a weapon. The Guests at the Gate is the war novel inside the empire-building story. It ends with a coronation nobody planned.