A backstory is almost as important as the main story itself. In fact, I would argue that it may be more important. Its presence can change the main story in profound ways.
I recently returned to The Adventures of Aura Lockhaven following a six month vacation, during which I worked on an epic fantasy arc.
For the epic, I wrote a backstory. Epics require backstories of, well, epic proportions. They have to explain the rise of empires, the clashes of kingdoms, and include sweeping curses and unavoidable prophecies. Otherwise, they just don’t satisfy. That backstory ended up being a twenty page journal of one of the original participants, explaining a war within a war within a war.
When I returned to Aura, I realized that her story did not have a backstory. She had a backstory, and so did her country, but her magical order just existed. I decided to change that.
As the Aura Lockhaven series is a set of standalone adventures centered around one character, the backstory for the Order of Enchanters needed to be more intimate than that of an epic. I decided on a generational clash within a family that affected her entire order, eventually affecting her. A mere three pages did the job.
That one backstory changed the tone of the first novel, and the entire planned series. Before, The Valley of the Mystic Moon was a charming romp, in which Aura undergoes nine tests to become an enchantress. Now, with that backstory in place, it’s far more somber and dark. The Order of Enchanters is listless and dissolute. The rest of Ayrdland believes the enchanters are extinct because they’re too busy drinking, humping, and fighting each other to bother with the outside world, all because of that family squabble. Aura really doesn’t want to become involved with them, but they can help her achieve her goal of being a better magician for her village. Now, I have some genuine conflict, other than a duel with the villain and fleeing from trolls. The nine tests structure no longer works. In its place, a new one is rising. In the process, the other characters changed to fit. Some became more serious. Others became more humorous. Others became more diabolical. Still others moved from far in the background to up front.
In other words, it is a far better book now, all because of that little three page backstory.