This is just astronomical nonsense. You surely won't use it unless your story mutates into a trilogy or worse. As I won't get rid of certain ideas until I write them down, here it comes. Ignore freely.
The lunar phases are merely the way one sees the moon from a certain place. There is nothing magical about it. But maybe, unce upon a very long time...
There was a planet, rich with magic, having its place in the universe. Somewhat later a smaller body approached, to become its companion, to leave it alone, or to destroy it. As it came near, great magical powers came into existence, drawing both bodies nearer and repulsing at the same time. The powers came fast to an equilibrium, making the smaller body the moon and changing the planet itself on the spot where it was nearest to the moon at the moment of the magical discharge. The flow of magic in the planet got a bit unstable.
The moon made his round, the discharge happened again. This time it took longer to stop, and on another place. So it happened over and over, till the whole planet had a ring of changed material, corresponding to the path of the moon over it. It was in this ring, where all the dragons awaked, there where the remains of powers concentrated into eggs.
You may ask yourself why there are only so much dragons, not 100 or 1000 or a more? Easy to theorize, theirs number is same to the number of days, or more exactly nights. All of these events happened at nights over the respective places. Maybe the sun disrupts the magical flow, who knows...
Conclusions:
- it may not be true the dragons hatched at the same time, nor that they are about the same power level. But it can be, it's magic.
- the ring they were born in is their natural living space, where they feel comfortable
- they must stay in the ring for the most time. Not only does it get uncomfortable outside of the living room, but they also channel the remaining magical forces that still flow between the planet and the moon. If there are too few or too many in any part of the ring, the moon could just float off or destroy the planet, literally. Talk about responsibility!
- they are essentially prisoners, with only short times to go where they please. So they cannot be much social even if they want, and must cooperate with others even if they don't want to either.
- the dragons may actually grow weaker if they leave the ring
- the ring they live in is a magical location, place where humans can access magic easily. But few dragons tolerate this.
- creation myths might be a re-telling of what really happened, something about meeting of two gods in the emptiness, and after a conflict falling in love, etc...
- speaking of mythology, imagine for a while that the planet and/or moon themselves were living or even sentient entities...
- the moon has a mighty impact on magic, in many ways. Maybe all people's powers change with the moon's phases.
- the night was always more associated with magic and unntatural happenings. Illusion at day, magic at night. The sun could hamper it through day.
- the movement of the moon is a constant through all the ages, except for a few extreme situations
- the dragons surely found a way to communicate across vast distances. Say it is like...
A chat-room!
The apprentice tries for the first time the spell of Read Minds on a little rabbit. Unfortunately, he just stands on-the-line between two angry dragons. "Seems like he likes that carrot" he smiles. Suddenly there flies a thought heavier than a bulldozer and splatters him : "Shut up!" A fit of epillepsy at 16. Life is hard for magic-users. 
- it is hard to learn about humans, even if you can fly around the world in a day:
You get many sights, but few insights.
