Dragons lived happily under Draco, the first king. They discovered portals leading all over the universe. Dragons did not make all of the discoveries. The most important of all the portals was the time portal to Earth. Dragons used it constantly to choose riders.
Draco, sitting on his grand throne, had an idea. Since dragons and humans are together so much, why not turn one into the other?
He sponsored a group of dragons to conduct the experiments. These dragons searched out humans, eho were then taken to the palace. The dragons extracted a sample of DNA from each of the humans. Volunteers then had the DNA injected into them.
The effect was not what the good king had hoped for. Instead of turning the dragons into humans, the DNA corrupted them, turning them evil.
The experimenters then tried the opposite: instead of turning dragons into humans, they were going to try turning himans into dragons.
The experimenters pulled samples of their own genetic material and injected it into the humans. It started out as a success. The humans began to change into beings that looked similar to dragons. When the experimenters asked the subjects how they felt, the creatures revealed their twisted minds.
Draco was disappointed to learn that the experiment had failed. He exiled the demos to a corner of Eden that was surrounded by a harsh desert. The demons have never forgiven the dragons for exiling them. As a result, the demons declared war on the dragons. Every kind of being was forced to take sides. Most sided with the dragons. The war has never stopped. It has now gained a new front: Earth.
The demons are striving to control all of the universe, even humans.