As the forces of loyalists and traitors clash on a thousand battlefields across the galaxy, a very different war is being waged in the shadows - a war of cunning and subterfuge, unknown to many, but undoubtedly playing a key role in the victory of one of the sides. Rogal Dorn and his Legion prepare to defend the Solar System from the armies of the Warmaster Horus, while Malcador the Sigillite sends out his agents and spies on missions of the utmost secrecy. Invisible hands are shaping the future of the Imperium...