Maggard was the golden-eyed bodyguard and house serf of the noble-born Terran Remembrancer Petronella Vivar who came aboard the Warmaster Horus' flagship Vengeful Spirit in order to write the definitive biography of the great Primarch to add to his glory and her own. His vocal cords were cut out as House Vivar did not believe that its serfs should be able to voice their opinions to their betters, but he was a very formidable warrior in his own right and was an expert at wielding an ancient Terran blade of some renown. Vivar communicated with her servant using an unusual piece of ancient technology called a Mnemo Quill, which was psychically reactive and could literally transcribe Maggard's words down on paper as he had them. Maggard hated his mistress who he considered an insufferable, self-centred and arrogant spoiled brat and he ultimately betrayed Vivar by siding with Horus as the corruption of Chaos fully claimed the 63rd Expeditionary Fleet during the final days of the Great Crusade.
Maggard accompanied his mistress to the surface of the moon of Davin when the Luna Wolves faced the undead Plague Zombies of Nurgle that had infested the small planetoid at the behest of the former Imperial Planetary Governor of Davin, Eugen Temba. Maggard defended Vivar with such skill that he came to the notice of Horus himself. Unlike his mistress, Maggard had deep respect for the Primarch and when the Warmaster deigned to praise his skill, Maggard kneeled and offered his sword to Horus, effectively voicing his desire to serve the Primarch over all others.
Maggard did not lift a finger to save his mistress when Horus murdered her so that she could not reveal the secret of how he had been corrupted by the Chaos Gods and the deal he had struck with them in which they promised to support him in his bid to overthrow the Emperor of Mankind. The Warmaster's Apothecaries in the Sons of Horus Legion performed genetic alteration and surgical enhancement procedures upon Maggard that allowed him to mimic some of the size and strength of true Astartes, so much so that his previous suit of personal armour no longer fit, and had to be reshaped by the Legion's artificers. After these changes, Maggard served as the chief enforcer for Maloghurst, Horus' Equerry and spymaster. In the course of these duties, Maggard ran afoul on the Vengeful Spirit's flight deck of Captain Iacton Qruze and the Remembrancers Euphrati Keeler and Mersadie Oliton as well as the Iterator Kyril Sindermann whom Qruze was leading to safety from Horus' slaughter of the other civilians aboard the flagship. The old Astartes became locked in combat with the silent assassin and was losing the contest when Sindermann picked up Maggard's pistol and shot the powerful man with it, wounding him. This gave Qruze the chance he had needed to end the massive assassin's life by stabbing his blade through Maggard's chin and up into his brain, bring his life to a close as silently as he had lived it. Qruze and the civilians then fled the Vengeful Spirit for the frigate Eisenstein and ultimately left the Istvaan System and its horrors behind to successfully warn the Emperor of Mankind of Horus' betrayal.
- False Gods (Novel) by Graham McNeill
- Galaxy in Flames (Novel) by Ben Counter