The Drakkar Heresy

"I, Urogar Thoric IV, thrice-blessed by Tyr, do declare, as Holm is my witness, that the beasts heretofore known as -REDACTED- shall be stricken from the records of our fair Nation, that all Holmgardians be forbidden from speaking their name or engraving their image or recording them in runelore. I declare that all -REDACTED- and -REDACTED- be driven out with axe and torch to the borders of our realm on pain of death. I do declare that all imagery of -REDACTED- be destroyed and all existing runelore pertaining to -REDACTED- be stricken. I do declare that the thrice-blessed order of Tyr be responsible for carrying out this most just Edict of Cleansing."
- Preamble to the Edict of Cleansing, engraved on the Pillar of the Laws in Carovin and the Imperial Lawstones in Holmgard
The Drakkar Heresy was a 50 year long period of strife in the Holmgardian Empire around the end of 4th century HR caused by the spread of a dragon-worshipping cult based in the ancient Imperial capital of Drakenhelm. The decades of intermittent purges, skirmishes, and outright wars of the Drakkar Heresy presaged the turmoil of the latter years of the Empire, and turned the Tyrian religion towards conservatism.
The Flight of the Golden Dragon:
As the Empire reached the height of its power, an ancient evil rose in the west. An army of vampires, human thralls, and undead, led by the order known as the Calabim, marched on the three westernmost realms of humanity. Swept up in their expansion was a colony of golden dragons, led by an Elder Drake called Aurenthakar. Aurenthakar was cruel, greedy, and arrogant, but even he could not resist the Calabim. So he took to the skies, flying towards the rising sun.
Aurenthakar and his surviving progeny fled to the east, migrating along the Balinok and Irontooth mountains over a period of decades. In the guise of various seers, he travelled the lands of the Empire. He spread the seeds of a prophecy - that Tyr, patron god of the Holmgardians, was about to return in the guise of an ancient dragon.
Tyr Reborn:
When this prophecy reached a feverish pitch, Aurenthanakar transformed into his true form and made a "miraculous" appearance in Drakenhelm. In mere days, the High Priest of Tyr in Drakenhelm and the majority of the city's population worshipped him as the living embodiment of Tyr. In weeks, most of the north had entered the fold.
Emperor Deuron, away on campaign in the west, had little choice but to acquiesce to the cults demands and allow them autonomy, unwilling to risk the wrath of a dragon on a second front. In the following years, the Drakkar faith would continue to spread, Aurenthakar gaining ever greater power and demanding more and more of the Emperor. Several small-scale wars flared during the reigns of Deuron and Haldemar, but the Drakkari were undefeated, cementing their position further.
The Draconic War:
Finally, during the reign of Thoric IV, the Drakkar movement reached a tipping point. In the 10th year of his reign, as Thoric led an expedition into the dreaded Greatwood, Aurenthanakar sent an envoy to Holmgard. He demanded that the Emperor himself bow before him as the living embodiment of Tyr. Thoric, in typical Holmgardian fashion, responded by beheading the Drakkari emissary and all his representatives in Holmgard, displaying their boiled skulls along the Path of Glory.
Aurenthakar responded with fire and blood. First, he ravaged the valleys of the Upper Meve, he and his kin incinerating dozens of villages. He torched Castle Graelingard, destroyed the cities of Jaln and Dagrenburg, and marched a well-armed force of heavily armed zealots towards Holmgard. But Thoric was prepared. In secret, he had been slowly assembling an elite force of adventurers, armed to the teeth with magic and weapons of dread power.
Aurenthakar arrived at the undefended city of Holmgard with much fanfare, and was pleasantly surprised when the city opened its gates to him. He was flattered by the welcoming crowds and heaps of treasure laid out for him in front of the Imperial Palace. But as he entered the Palace to fanfare, arrogantly striding through the doors by himself, a wall of force barricaded him in, and he was fallen upon by seven elite adventurers, supported by a cohort of crossbowmen. After a battle that destroyed the old palace of Holmgard, Aurenthakar fell.
Aftermath:
In the aftermath of the Heresy, all dragons, dragonborn, draconic imagery, and even mention of the word "dragon" was banned by Thoric in a vast act of damnatio memoriae, and dragons were wholly erased from Holmgardian culture. The surviving members of Aurenthakar' brood migrated east once more, to Lumeris...