Erebus held the prestigious position of First Chaplain of the Word Bearers Space Marine Legion during the rise of Horus to the rank of Warmaster and the end of the Great Crusade in the early 31st Millennium. He was a fearsome and intimidating Astartes warrior and wore tattoos depicting sections of the Book of Lorgar across his shaven scalp to terrify his enemies. Erebus was the first of the Space Marines to knowingly turn to Chaos and he was personally responsible for corrupting his own Legion's Primarch Lorgar, Horus and the Death Guard First Captain Calas Typhon to the worship and service of Chaos. Erebus is presently one of the ruling Dark Apostles of the Word Bearers Traitor Legion, and fights a subtle, but noticeable war against the Black Cardinal Kor Phaeron for control of the XVIIth Legion's direction in the Primarch's continued absence.
It is unknown when exactly Erebus turned to the worship of the Dark Gods, though it may have happened when the Word Bearers joined with the Luna Wolves to pacify the world of Davin mid-way through the Great Crusade. In any event, when his Primarch Lorgar grew angry with his father the Emperor after he was chastised on the world of Khur for trying to spread worship of the Emperor of Mankind as a divinity across the galaxy, Erebus explained to his master that there were other entities in the universe that were more than willing to accept his worship and the worship of other humans. Several years before the outbreak of the Horus Heresy, Lorgar and Erebus had fully corrupted the Word Bearers to the service of Chaos, even going so far as to erect temples to the Dark Gods on every world they brought into Imperial Compliance. Before long, the Ruinous Powers sought to act through Erebus to set their plan in motion to destroy the Imperium of Man and the greatest champion of Order in the galaxy--the Emperor of Mankind.
To achieve this outcome for his dark masters, just before the Imperial war with the Interex began during the final stages of the Great Crusade, Erebus began to have many secretive dealings amongst the Luna Wolves Legion and with the Warmaster in particular. In fact, it was he who sabotaged the peaceful negotiations precipitating the war between the Imperium and the Interex, by stealing an archaic Kinebranche Anathame sword from the Interex's closely guarded Hall of Weapons. This theft was not simply out of greed - it was all part of Erebus' carefully managed plan to corrupt the Warmaster and bring him under the influence of his own secret masters, the powers of Chaos.
By supplying the Anathame to the traitor Planetary Governor of the planet Davin, who was subsequently corrupted by Nurgle, Erebus hoped that Horus would be wounded by the weapon and put beyond the care of his Legion's Apothecaries. Once this had taken place, the grief-stricken Abaddon and Horus Aximand of the Luna Wolves' Mournival were only too keen to turn over their master to Erebus' care, and Horus was resurrected by the dark Chaotic rituals of the Davinite priests.
Erebus continued to pour honey into Horus' ear, manipulating the Primarch's arrogance, ego and desire for power and directing him further from the ideals of the Great Crusade into pursuing his own ascension to replace the Emperor as the Master of Mankind. By showing the Warmaster the powers of the Warp, and urging him to make pacts with the Chaos Gods, he eventually set Horus on the path to heresy against the Emperor. Along with Horus, Erebus masterminded the Istvaan III massacre of the Traitor Legions' remaining Loyalists, ever mindful of the need to eliminate those elements of the Traitor Legions who still served the Emperor before the war against Terra could begin. Captain Garviel Loken of the Sons of Horus suspected Erebus was a Traitor and a conspirator against the Imperium, which only led the corrupt Chaplain to add him to the list of doomed Astartes brethren who were to be caught in the virus bomb assault on the doomed world of Istvaan III. Erebus remained with Horus throughout the Heresy, acting as his dark spiritual adviser and co-conspirator. Erebus, however, only ever truly served the Dark Gods of Chaos.
Erebus is currently a Dark Apostle of the Word Bearers Traitor Legion and a member of the Legion's Dark Council, the ruling body of Sicarus, the Daemon World ruled by the Word Bearers within the Eye of Terror.
In Greek mythology, Erebus is the Primordial God of Darkness, and the son of the primordial entity Chaos.
- Horus Heresy: Collected Visions, pp. 126-127, 162-163, 228, 330, 360
- Index Astartes IV, "Dark Apostles - The Word Bearers Space Marine Legion"
- The Horus Heresy - Book Two: Massacre by Alan Bligh, pp. 138, 143, 155, 258
- The Horus Heresy - Book Five: Tempest by Alan Bligh, pp. 33, 139, 248
- The Thirteenth Black Crusade (Background Book) by Andy Hoare
- White Dwarf 270 (US), "Index Astartes: Dark Apostles"
- Horus Rising (Novel) by Dan Abnett, pp. 315-319, 326, 347-348
- False Gods (Novel) by Graham McNeill, pp. 31-32, 36, 42-43, 45-52, 54, 56-60, 76, 89, 103-106, 109-110, 112-113, 116, 132, 174-177, 191, 198, 205-207, 210-211, 260, 265-267, 271-273, 277, 293-295, 298, 341-342
- Nemesis (Novel) by James Swallow, pp. 13-15, 17-19, 244-245, 249, 273-274, 324-326, 354-355, 387-391, 404-408
- The First Heretic (Novel) by Aaron Dembski-Bowden, pp. 9, 61-64, 66, 68-73, 81-83, 88-89, 117, 159, 163, 166, 228, 269-270, 278, 295, 301, 318, 323, 361-362, 367-368, 370-371, 380, 382, 385-386, 393-394, 414-420, 432, 437
- Fear to Tread (Novel) by James Swallow, pp. 30-31, 90, 96-97, 111, 120, 151, 178-179
- Betrayer (Novel) by Aaron Dembski-Bowden, pp. 12-13, 78-80, 106, 112, 114-118, 123-128, 142-143, 149-153, 158, 169, 185, 196, 203-204, 209-210, 219-222, 227-229
- Vulkan Lives (Novel) by Nick Kyme, pp. 9, 210-211
- Dark Disciple (Novel) by Anthony Reynolds, pp. 13, 18-19, 21, 115-116
- Dark Creed (Novel) by Anthony Reynolds, pp. 4-5, 9, 22, 53, 56, 99, 102, 156-157, 159-160, 164, 167-168
- Forge World Horus Heresy Character Series - Erebus & Kor Phaeron