The Alpha Legion are devious beyond measure, but deceit is a double-edged sword. As the Indomitus Crusade pushes into the far reaches of the Ultima Segmentum, and Solomon Akurra and his warband the Serpent's Teeth encounter the feared Primaris Marines, the Alpha Legion is faced with a choice - fade into the shadows, or adapt and strike back.

Solomon intends to take the title of Harrowmaster and bind together the feuding heads of the hydra that make up his Legion, but his allies are disparate and unproven, and his enemies march with the might of the Imperium at their back. Much is not as it seems, and the odds are stacked against the sons of Alpharius... but Solomon is armed with a weapon the Imperium cannot ignore: the truth.