Lucion was the son of Mephisto (the Lord of Hatred) and a brother to Lilith, which goes by many names. In ages past, several hundreds of years before the events of Diablo I when Sanctuary was still a relatively young world, Lucion ruled the Triune in the guise of the Primus. As the leader of the Triune, Lucion fought a secretive and subtle war against the Cathedral of Light that would decide which of the two cults would eventually dominate the human race.
Some time after the creation of Sanctuary by the renegade angel, Inarius, the world was discovered by the Burning Hells. Realizing that a full scale invasion would inevitably draw attention of the High Heavens (which would very likely result in a heavy struggle that would devastate Sanctuary, rendering it useless to either side), the Lords of the Burning Hells opted for a more subtle approach. They devised a cult that would gradually lure its followers deeper into the darkness. Which at first seemed a harmless, peaceful cult turned out to be a dark, unholy sect devoted to the three Prime Evils. At the head of this cult stood the Primus, the pontifex maximus. However, the Primus was nothing but a façade, a disguise used by the demon Lucion.
The Triune soon grew to become one of the dominating cults of Sanctuary, being second only to the Cathedral of Light, the counter-sect led by Inarius in his guise of the Veiled Prophet. The two sects continued to vie for control over the human race but without any open warfare, as it would draw unwanted attention. Instead, Lucion and Inarius plotted against each other through subtle scheming, always anticipating their opponent's moves.
The Sin WarEdit
Their subtle plans were disturbed by the sudden reappearance of Lilith, a renegade demoness who had her own goals and plans. In the guise of the fugitive noblewoman Lylia, Lilith sought to awake the special powers of the humans (who were in fact the offspring of pairs of renegade angels and demons), harbouring it for her own goals. Her unwitting champion was to be Uldyssian, a simple farmer from the lands near Seram. Noticing Uldyssian due to his immense powers (after it was used to the detriment of several travelling missionaries) and quickly seeing his potential, Lucion dispatched his trusted lieutenant, the high-priest Malic to capture the farmer and his companions. However, unaware of Lilith's presence, the raiding party was overwhelmed and utterly destroyed, sending Malic back fleeing to Lucion. Realizing his sister could have returned, Lucion 'blessed' his failing lieutenant with a demon limb, allowing him to remove Lilith's guise.
After a second and much more powerful raiding party consisting of many undead morlu attacked Uldyssian and his followers near the town of Partha, but failed again (this time leaving Malic dead by the hands of Lilith), Uldyssian decided to leave the town, after seeing the onslaught. Lilith followed him, still in the guise of Lylia, but soon after their reunion Lucion's spell took effect, revealing Lilith's true form to a horrified Uldyssian. Lilith easily defeated the farmer, leaving him severely wounded. Still, Uldyssian recovered and reunited with his companions, setting out for the jungles of Toraja.
It was here that Lucion personally intervened. Disguised as a white stallion, the demon tried to lure Uldyssian with him but the latter was timely warned by his brother, Mendeln. Once again taking the form of the Primus, Lucion sought one more time to persuade the farmer to join him. After both attempts failed and Uldyssian and his gathering followers started attacking the demon, Lucion changed tactics. With relative ease the demon incinerated many of Uldyssian's followers and caused the latter's close friend Achilios to die by one of his own enchanted arrows. After seeing his comrade and followers die, Uldyssian's true powers awoke as he burst out in rage. Being unable to maintain his position, Lucion finally revealed his true form: a horrid, reptilian demon with hooved legs and three tails, covered in thick scales. But even as a mighty demon, Lucion turned out to be overpowered by the sheer force of Uldyssian's abilities. As a last desperate act the demon even offered his obedience and subservience to the farmer, but all for nought. Instead of killing the demon, Uldyssian simply imagined the demon to be nothing, and so the great Lucion faded away and disappeared.
- The name Lucion is possibly a reference to Lucifer.
- In the Sin War novels, Lucion, along with Lilith, is described as having an overall reptilian appearance. The Book of Tyrael includes an illustration of Lucion that gives him a corpse-like appearance similar to Mephisto's. Prior to the sourcebook, Blizzard did not have a strong idea of what Lucion should look like. His image was designed by Jean Baptiste, a freelance artist.
- Lucion's image is eroneously used to represent Mephisto in the latter's Heroes of the Storm reveal trailer.