65 million years ago, before the other races existed, dragons were Gaia’s original progeny. The dragons were very powerfully psionic (compared to the "lesser races"). The Destroyer came to Earth, and the dragons acted quickly to save the earth.
They performed some sort of huge psionic ritual, the end results of which are: a new mobile planet, twice earth gravity, for the few surviving dragons to use to mislead the Destroyer, leading it away from Earth; the asteroid belt (debris); Gaia’s injury, resulting in her largely beginning anew (although scarred, and leaving her barren in a sense, since she no longer produces creatures on par with the power of dragons); the deaths of most dragons, leaving behind their bodies for the fossil record.
So, 65 million years later, the dragons have evolved into the multiple color types, and live on their own world ("Dragonstar"), continuing their nomadic lifestyle, running from the Destroyer, which constantly pursues them. It is the only reason Earth has not been noticed yet since its restoration.
The Destroyer has been pursuing the dragons for so long, the essence of dragons has been firmly imprinted into it. It is very sensitive to all dragons, and is able to follow where they go. When Eva’s character travels to Earth, this shifts the eye of the Destroyer to that world, and it begins to notice what is happening with nearby magically seeded worlds. (Although the Caretaker being more powerful even than the sum of its parts has really drawn the Destroyer’s eye, so it’s not actually Eva’s fault.)
Legend says if they ever stop moving, the Ancient Wyrm, a terrifying dragon with seven heads, with come to swallow their world. Indeed, history records that in the past when the world has been stopped for any length of time, psychic shrieks sound and everyone is overcome by waves of fear and loathing.
The legend says that long ago, they were cast out of heaven, but when a dragon leaves this realm, he returns to heaven in spirit.
Leaving Dragonstar is a social taboo; dragons are not supposed to leave. The religion speaks of not only disgrace but ultimately destruction for those who leave the protections of their world.
Dragonstar has awakened, and largely moves itself around now, so that the dragons don’t actually have to do it.