"All is dust..."
- —Book's tag-line
A Thousand Sons is the twelfth volume in the Horus Heresy series of novels.
Censured at the Council of Nikea for his flagrant use of sorcery, Magnus the Red and his Thousand Sons Legion retreat to their homeworld of Prospero to continue their use of the arcane arts in secret. But when the ill-fated Primarch foresees the treachery of Warmaster Horus and warns the Emperor with the very powers he was forbidden to use, the Master of Mankind dispatches fellow Primarch Leman Russ to attack Prospero itself. But Magnus has seen more than the betrayal of Horus and the witnessed revelations will change the fate of his fallen Legion, and its Primarch, forever.
Following a reprimand by the Emperor of Mankind for dabbling in psychic sorcery, the Primarch Magnus the Red and his Thousand Sons Legion secretly continue to study sorcery despite being forbidden to do so. Magnus learns through the power of the Warp of his brother Horus' impending betrayal, and tries to use his psychic abilities to warn the Emperor on Terra, hoping the news would justify his disobedience of his father's edict against the use of sorcery. However, Magnus overreaches with his powers and causes damage to the vital and secret attempt by the Emperor to create a human extension of the Webway deep beneath the Imperial Palace, opening the path to a daemonic invasion of Terra itself in the process. The Emperor is enraged and orders Leman Russ and his Space Wolves Legion, accompanied by other Imperial forces, to bring Magnus and his Legion to Terra to account for themselves, initiating the chain of events that will lead Magnus and his Thousand Sons to become the servants of the Chaos God Tzeentch.
- A Thousand Sons (Novel) by Graham McNeill