I'm sure that most new authors would say the same: the story I started out to create is not the story that I finished. It's not even close. The only thing that remained the same was the character's first name.
I originally created Areia to be a girl with nothing left to her name but a desire for revenge, who hunts down and trains with a fabled assassin master. Revenge for what and against who? I never figured that much out. I wanted Areia to be emotionless, able to kill without a lot of thought behind it. Eventually, she would have more assignments than she could complete, working in a ruthless society set in a hot, desert location. Her main struggle would have come from when she started to care and when vengeance just wasn't enough.
Instead, what I eventually settled on was an emotionally charged girl who is gifted with magical powers and becomes part of a society of women bent on saving and protecting a Empire that is rotting from the inside out—in a nice, pleasant environment with lots of trees and beauty and a history of very little violence. Areia's main struggle comes from within, which is the same, but it has to do more with finding out who she is, finding a sense of belonging and balance in her life.
I had this great in media res beginning, too, with Areia lurking in her victim's office, waiting to kill him before slipping out. I also had a horrible analogy between her and a vase, but that could have been improved on. I expected a short story, maybe 250 pages or so. Possibly a series, but most likely a stand-alone.
It's strange what can change in the course of writing a book.