The original source of evil and sin in the AoD Universe, the Original Sin is a blight that spreads the infection and imperfection of life throughout existence. Its power over evil is stronger than the Primordial of Evil, Hebi itself.
The origin of the dragons comes back to the foundation of life on the worlds themselves. There were once two races, the Dragons, created by the Primordial of Order, Umetherial , and the Dijra , human like beings which would become the template for gods later, created by the Primordial of Chaos, Apothis .
Apothis, not being one to like such things as Order, wanted the two races to destroy each other.
To this end, he convinced a young dragon to attack the Dijra. Upon doing so, the two races began to slowly escalate into a war that would put the gods and their current conflicts to shame. Upon Umetherial realizing what had happened, he had no way to describe the willing desire to destroy other life the young dragon had within it, so he gave rise to two new Primoridals, the Primordial of Good, and the Primordial of Evil. He then scattered both the Dijra and the Dragons across the universes, cursing all of the dragons who willingly followed the Young Dragon into mutated, impure forms. The Young Dragon was given a far worse fate. He became the Primeval Sin, a hideous black dragon who would represent the purest form of wickedness and malice, ridden of all mind and reason.
All the dragons that still chose to follow Primeval Sin became further cursed into the Accursed Dragons, who to this day continue to wreak havoc across the worlds.