For a story that I have been working on since 2012 - a lot. The plot originally was pretty generic and cheese rebel story in a made up country, inspired bt Italy and no magic involved.Then I added more political drama - no outher force interfiering, rather the fear of it taking advantage of their situation and attacking any moment, as well as family drama - family at ruins, the siblings separated and taking different paths only to be reunited later on but not knowing that untill later on and that was one very teary and cringy reunion. Some of the characters were changed a lot as well - Delyana went 180, because at first she was one of the main villians, while now she is a mojor ally, her relationship with Asya also changed, because obviouslly they were mortal enemies at first. Their names were Desdemona and Arabella originally, but when I started shifting towards Slavic inspired lore and culure I changed the names of almost every character.And with that change of "source"the plot evolved quite fast - romance took a secondery role, while family bonds are the main driving force in the plot. Magic appeared and evolved as well, with the creation of the types of witches and why they were immortall and how they felt about it.
The original ending is now the ending of the first part and that too chandged quite a lot - who lives, who dies, who marries who, what rank they have...
Many of the characters, even though antagonists, have reasoning behind it, not "yeah, I am bad and I want power because of it", so they are not so much of a villian(at least in my opinion), besides some people in later part.