In reality.... Nothing.
But in the book that Dark Shadow is talking about The author claims that all ley lines are the migrational paths of dragons or some such. It's been a number of years since I read the book. Of course she also claims that a witch can "own" dragons and that they will do her bidding as long as she keeps them happy.
I kept thinking... Why would any creature that had watched mankind crawl for the ooze, and make such a mess of the world, tolerate our existance? Much less become subjugated to us?
They watch us from the astral planes and choose to interact with a few, but they come and go as they please. They will act if asked but they are never "property" and they watch out for us not the other way around.
GRRRRRRRR!

That particular attiude about dragons makes me very angry.