Synopsis:
Ahriman of the Thousand Sons follows a vision that is not his but sent by the Psychagogue, a herald of Tzeentch, in which the daemon promises him help in locating clues in his search of another Webway portal. When the Sorcerer arrives at the cardinal world Reliquitus the daemon asks for a favour in return; for the failure to subjugate the Exodite World, Song of Isha, it has been trapped inside a jade mask and can now operate in full only through the wearer of the mask. The population of Reliquitus knows this mask from local legends as the Mask of the Emperor, and this incomplete and misleading lore lures a local cardinal to put it on after the recent discovery of the lost relic'. Unfortunately, the cardinal's mind and body are unfit to sustain the daemonic essence, and that is the favour the Psychagogue asks of Ahriman - to find a vessel strong enough to host it. Only then it will reveal the promised clue, the location of Moriana, who, as the daemon remarks, seems to know more of hidden ways than Ahriman. The daemon further taunts the Sorcerer by hinting that Ahriman's inability to discern the route to his ultimate goal is caused by the divergence of his purpose and that of his Chaos master.
Jacques Gozier, an Ordo Hereticus inquisitor, and his retinue are sent to return the desecrated relic, and among them Ahriman will find a candidate to host the daemon. Gozier himself is problematic to reach due to the protection of his psychic hood and the daemonhost he commands; but the interrogator from his retinue, Amelia Russel, and Fiachra, the Blood Raven veteran leading the inquisitor's kill team, are the two most convenient targets.
Amelia and the kill team are ordered to reclaim the alleged Mask of the Emperor but is ambushed by the cultists now swarming the capital city of this world. While the kill team warriors fight the mutated worshipers, Ahriman transfers the interrogator into the temple where the Psychagogue has made its lair. The young woman, strong-willed, ambitious and hungry for knowledge to the point of obsession, is rejected by the daemon, who states that there is another role for her in the forthcoming events. It advises Ahriman to promise her tutelage in the arts that have allowed the inquisitor to bind the daemonhost to his will, and as the Sorcerer agrees, the woman, not knowing his true nature but recognising only his immense power, greedily accepts the offer to serve a new master.
The second target, Fiachra, is currently shielded by the presence of the inquisitor and his daemonhost, which interferes with Ahriman's sorceries. Open confrontation is inevitable, and moreover, the Psychagogue is unnerved by the nearness of the Nurgle-spawned essence inhibiting the daemonhost. This entity that calls itself Tuberculosis has strength to pit against that of Tzeentch's herald, and Ahriman is left to battle Gozier and his retinue on his own while two daemons clash. The squad of Rubric Marines he has been able to summon to his aid confront the remaining Imperial forces assembled by the inquisitor, while Ahriman aims for Gozier himself. He manages to mortally wound the opponent, but as the psychic protection around the inquisitor begins to fade, Ahriman is attacked from his back by the Callidus assassin Gozier has earlier dispatched to assume the disguise of a mutant cultist and secretly approach the enemy. It is then that Amelia fulfills her role and saves the life of her new teacher by taking the shot aimed at him. Severely wounded, she can only watch how Gozier dies, and with his death nothing prevents Ahriman from using his sorceries to the fullest.
As the Imperial forces dwindle, Ahriman neutralises the assassin and attacks Fiachra - only to witness how in the battle of daemons that has raged all the while the current body of the Psychagogue is torn apart, and the jade mask cracks in two. Ahriman sends a wave after wave of psychic energy surges to strike at Tuberculosis, but the daemon retaliates and throws the Sorcerer across the hall to where the remains of the defeated herald lie, and Ahriman's hand touches the broken mask. Fiachra, sensing his opportunity to finish off the enemy and, taking off his helmet, faces Ahriman, who stands up to fight. Parrying the attacks with his staff, he manages to bring the half of the jade mask to Fiachra's face, and the Psychagogue claims his body. The inquisitor's daemonhost is no match to the possessed marine, and once the herald of Tzeentch is victorious, it fulfills its part of the deal and returns to Ahriman something that he has considered long lost, something that will enhance his vision and show the road to Moriana and eventually a Webway portal; a crystal from the Reflecting Caves beneath Tizca.
