An Athame was a unique ritualistic dagger made from crude metal or flint that was blessed by the Dark Gods and possessed the ability to alter the very fabric of reality. Athames were utilised by the Word Bearers Traitor Legion during the Battle of Calth in the opening days of the Horus Heresy in the early 31st Millennium. These eight so-called Shards of Erebus were esoteric weapons crafted from shards of the daemonic Anathame that had mortally wounded the Warmaster Horus on the plague moon of Davin and had facilitated his conversion to the service of Chaos in the Temple of the Serpent Lodge. Athames possessed special properties that enabled them to rend the skein of reality, allowing the wielder to step through the Immaterium and cross vast distances in realspace, whether aboard a vessel traveling through the Warp, or even onto another planet in the galaxy. Unknown to Erebus, the Athames could even allow their users to travel multiple millennia back in time. Several of the XVIIth Legion's mortal Chaos Cultists on the surface of Calth also utilised ritualistic weapons known as Athames, though these were rather small, mundane versions of the weapon, which was made out of flint or crude metal. Blessed by the Dark Apostles themselves, these daggers were considered a mark of high status within the ranks of both the XVIIth Legion and its allied Chaos Cults. The whereabouts of the Shards of Erebus following the Battle of Calth is unknown, although one Athame is believed to have been used by the Inquisition during the Pandorax Campaign's Battle of Pythos to seal the Damnation Cache.
To further the cause of Horus' rebellion, the Word Bearers' Chaplain Erebus had interpreted the will of the Chaos Gods and devised the means to achieve his lofty goals. The Dark Apostle took the Kinebrach Anathame, the daemonic blade that had mortally wounded Horus and begun his corruption by the Chaos Gods in the Temple of the Serpent Lodge, and prepared to perform an ancient ritual. Within his personal chambers aboard his flagship, the Destiny's Hand, Erebus presented the sword to the statues of the four Ruinous Powers, calling out prayers and incantations, saluting the dread lords of the Warp, each in turn. He had the doors to this chamber barred and his bodyguards standing watch outside. Cowled artisans stood ready at the Dark Apostle's side -- Guldire, chief among the Erebus' Warpsmiths, shadowed by his foremost apprentices. Though it seemed a sacrilege to do what he must, the weapon had already served its purpose -- in this form, at least.
Utilising a rune-inscribed hammer from an apprentice Warpsmith, Erebus brought the hammer's head down and began to reforge the baleful weapon into its new forms. With each dolorous hammer blow, the Dark Apostle was able to break off a finger-length sliver of the blade's weird alloys. Though diminished, the Anathame was yet whole. Seven more times did Erebus break the dark blade; seven more shards were commended to his Warpsmiths, until finally he was done. The shards had been knapped from the blade by his own hand, in accordance with the old rituals. Then they were grown in the blood of the Neverborn, and fashioned into fine implements – each alike, but no two exactly the same. The fracturing of the Anathame was but the first step down a longer path. The diminished blade would be disposed of as the Dark Apostle had originally been instructed.
Six daggers were forged from the metal taken from the Anathame for those Word Bearers who would lead the assault against the Ultramarines Legion on Calth; Dark Cardinal Kor Phaeron, Chief Librarian-Sorcerer Quor Vondar, Phael Rabor, Morpal Cxir, Foedral Fell, and Hol Beloth. The seventh was to be carried by Sergeant Kolos Undil, the leader of Erebus' cadre of bodyguards. The eighth and final dagger was forged for himself. Each of these servants of the Dark Gods could feel the untapped power that emanated from the dark blades. These were no mere ritual Athames, but true tools of the Gods. Although all the blades were similar -- hilts bound in black leather or wire, marked with golden runes and tied with devotional ribbon -- the blades were all markedly different. Crooked, or straight, one forked, another with waved edges. All were, however, of the same flinty black metal that pained the eyes. Though initially insulted that the bearer of one of these daggers was a mere sergeant, Erebus assured his fellow Word Bearers that Undil's possession of one would not diminish the potency of the rest, nor the honour in carrying one. Undil was a renowned warrior within the XVIIth Legion, as devout as his master and almost as devious.
Erebus informed the bearers of the Athames that the blades were gifts of the gods. They possessed the power to shield the wielder from harm, or to aid him in the working of great sorceries. However, these esoteric weapons were dependent on the ability of he who carried them. These Athames were not merely ritual tokens, but tools of enlightenment. A wound from them could turn the mightiest Loyalist hero to the Traitors' cause, opening their eyes to the majesty of Chaos, and the perfidy of the Emperor. If the Word Bearers Primarch Lorgar intended to rid himself of Erebus, then he would be disappointed. That the eight Shards of Erebus now also offered his fellow commanders the opportunity of escape from Calth was unimportant to him. Whether or not they would learn how to effect flight through the Immaterium using the artefacts should they need it was something he would leave to the will of the gods.
During the Battle of Calth, the Ultramarines 4th Company, under the command of Captain Remus Ventanus, converged on the fortress of Leptius Numinus. The Loyalists were able to power up the palace's data-engine and Vox assembly in order to contact other possible surviving Ultramarines, Imperial Army or Loyalist Mechanicum forces. Ventanus eventually established short-range communications with other besieged Ultramarine units. His situation was not unique. All of the Ultramarines on Calth's surface found themselves mired in the same predicament. Soon a large horde of Traitor forces commanded by the XVIIth Legion's Commander Morpal Cxir encircled the palace and launched an attack against its small group of valiant defenders. Terrible carnage was inflicted upon the Loyalist defenders by packs of horrific daemons summoned from the Empyrean as they punched through any breaks within the defensive line. During the ensuing battle, Captain Ventanus unintentionally utilised the Athame taken from Morpal Cxir in an earlier skirmish, and defeat the daemon Samus with it. At the time he had no other weapon at hand, and was amazed by the blade's lethal potency. When his sergeant, Kiuz Selaton, suggested gathering other such similar blades from the fallen Word Bearers and their human servants to utilise against the hordes of daemons that now ravaged Calth's surface, Ventanus wisely refused. But he did keep the Athame he had used and placed it safely in in his belt.
At the climax of the Battle of Calth, Primarch Roboute Guilliman personally led his Suzerain Invictarus and whatever supporting Ultramarine forces he could muster to assault on orbital platform controlled by Kor Phaeron and his elite guard. The Dark Cardinal and his warriors each carried an Athame dagger. When confronted by the Primarch in personal battle, the Dark Cardinal was able to stun the Primarch utilising the fell powers granted to him by the Chaos Gods. Rendered temporarily helpless, instead of killing the Primarch, Kor Phaeron toyed with the idea of using his blade's innate abilities in an attempt to turn Guilliman to their cause, as Erebus had already done with Horus. Though he held the blade to the Primarch's throat, piercing his flesh, he was unable to strike a fatal blow. Guilliman was able to resist the dark influence of the malefic blade and launched a lethal counter-attack of his own, impaling Kor Phaeron through his chest with his inert Lightning Claws. This mortal blow forced the Dark Cardinal and the Word Bearers to retreat.
- Know No Fear (Novel) by Dan Abnett, pp. 58, 93, 200, 259, 294-295, 299, 305, 310
- Mark of Calth (Anthology) (Digital Edition), "The Shards of Erebus" by Guy Haley, pp. 8-23
- The Chapter's Due (Novel) by Graham McNeill
- Perpetual (Audio Drama) by Dan Abnett