Once upon a time, as the stories have always gone so this one shall be.
Once upon a time there was a fairytale world. A world created by the gods. Where the creatures they created could live, and fall in love. A land of happily ever afters. It seemed that this world would be the perfect place for their creations, but there is one thing the creators forgot. And that was that for every good there must also be evil.
Peace could not be without balance, and not just a balance of magic and nonmagic, but also a balance of good and evil. And so evil came to be. Being born of the nature of living beings to be jealous, and vindictive. Born of the nature of living beings to want revenge. The Shadowhunters were created, to keep magic and evil in check. To be sure that magic and evil did not encroach too much on those without magic and those who were good.
With the beginnings of evil came the first fairytales. The stories that lead to the Golden Age of the kingdoms. Those tales needed the adversity that evil brought them to create heroes out of every day people. For without the trials of evil, there will be no heroes. The Golden Age seemed to everyone to be the end to wicked witches, and evil stepmothers. It seemed to be the beginning of happily ever after for all of the kingdoms. But happily ever after didn't last as long as they'd thought.
Another witch, an even greater one than all those who had come before her cursed the kingdoms, vowing to have revenge upon the children, grandchildren, and great grandchildren of those who had ruined all those who came before her. She cursed a book of fairytales making it so that all of the stories which had lead to the Golden Age would repeat themselves. Over and over again. Becoming more and more twisted the longer time went on. And every time these tales would end unhappily, in fact, the only way to break the curse is for them to end happily.
Generations later the fairytales have become almost twisted beyond recognition, and those whose ancestors lived during the Golden Age are forced to relive the stories that made heroes out of their ancestors. The trick is to make it out happily. Because in the fairytale world you live happily ever after, or you die.