Darcio was the remaining dragon of royal bloodline, which were called the Haciendas. The red dragons had been the most powerful for centuries, especially of pure bloodline because they could control both the flame.and frost powers. As the remaining King of red dragons, Darcio was a proud man who thought he deserved to rule over the world.
He desired to be worshipped and praised by everyone, and he didn't want to see anyone above him. Anything he desired he got. Whether it was women, land, rulership. He wanted everyone to surrender to him.
This led to him conquering the black and white dragons in battle and he became King of all dragons. They all bowed to him and he killed off anyone who showed any rebellion. He made sure to eliminate the existing generation of all royal bloodline dragons so they wouldn't pose any threat in the future. Darcio ruled for centuries. The three dragon clans had many accomplishments under his reign, despite his terrible ruling.