The Black March

During 4,891 AR, Gladrung was the firstborn of the Celestial that grew to loath the lesser races for their ceaseless cycle of pain and hatred after the direct intervention of the Wroth Daevatan family sewing discord in her heart. Taken over by nihilism she sealed her mother and rampaged across Zaria sparing only the Drakonian's that worshipped them in "perfect order" (ie. a strict caste system that you die if you go against). She nearly killed Lacdu destroying his mana core. Calling forth the wrath of Avengel Caduceus, Tamenthil, Elendil Pendragon, The Black Hound and Merlin. Culminating with Merlin warping her away seemingly "sacrificing himself". But no one knows where they truly went, or if either really died.
The other heros all having suffered some form of loss, be it Lacdu's mana core shattering, Avengel suffering a critical injury and being forced to rest for hundreds of years, or Tamenthil burning a significant portion of her divine power and "splintering". Though worse was the two casualties, Merlin's mysterous dissapearance, and Elendil Pendragon, heiress of House Pendragon's death--and her very soul being devoured. Driving the Black Hound to earn his title in his decent into temporary madness and depression.
This lead to the mass slaughter and hunt of the Dragons upon Zaria and the general cultural fear against the creatures, as the peoples views of the creatures became twisted by terror. All to the plans of the Wroth whom wanted the most powerful threats they faced on the surface to be driven back by the very species they had been protecting. When the Thousand-Year Blood War ended, the first major edict of the Ceridian Empire was a Empire-wide hunt for the beasts seeking out their blood and bodies to restore lost resources that the war cost the various nations.