Dread Dragon (conceptual lore)
All Dragons were created by The One with the purpose of safeguarding the mortal realm, but when the banished gods betrayed him and tried to take the mortal realm from him, some dragons also turned their backs on their creator. Those that were not destroyed fled alongside their new masters to the Dark World where they became the apex predators of that accursed realm. Over the thousands of years they resided within the dark world, the dark magics that swirled in the air became imbued into their flesh and bone. Their bodies became slenderer and sleeker, abandoning the raw bulk and power of their brethren, their scales grew more bladed, their wings grew more claws, their breath turned to dark plasma that both vaporized and rotted living flesh, and their once noble minds grew twisted with hatred for the world they were once sworn to protect.
Just an idea I had and scribbled a quick concept of for my setting.