I read a fanfiction a while ago (probably at least five years ago) that I can't seem to find. Note, that I don't actually want to read it; I'm only asking about it because I find it mysterious that I can't find it. So if you can answer the question without providing a place to read it, that is fine.
The basic thrust of the story was that Ginny had to be sent to America for school. I'm pretty sure this was because she was expelled from Hogwarts for her part in the Chamber of Secrets incident. The story follows Ginny as she travels to America and goes to a new school.
I believe I read it on Mugglenet
The story was reasonably long (a whole bunch of chapters, I think).
There was an older girl in Ginny's new school named Esmerelda.
They were very into dueling. There was some kind of inter-school dueling tournament, and Esmerelda was a champion dueler.
The head of Ginny's new school was a woman.
There was a man who I think taught at the school, who was a very powerful wizard. There may have been some backstory with him having been an Auror or something in Britain but getting banished for some reason.
There was something going on between the above mentioned man and the headmistress of the school, like being secluded alone in her office late at night for long periods of time. At first people suspected that it was an affair of some sort (I'm not sure if either of them were married), but it later turned out that they were practicing to make the man invincible (more on that below).
I believe the man was the leader (or at least part of) some elite group of wizards that besides for being exceptionally good at magic were also well-trained in non-magical combat.
I think the man was a friend of Dumbledore, and I have some vague association of him with Kingsley. Maybe he was Kingsley, or a friend, or I might be misremembering.
There were various types of magic invented for this story that do not exist in the real Harry Potter stories.
I think there was some type of travel that involved waypoints in the air that could transport people in a portkey-like manner.
There was some type of magic/spell that could create a zone where no magic could be performed. This was integral to the story, as one of the tactics used in the major battle against Voldemort was to make the area a non-magical zone and then rely on their non-magical fighting skills. There was something about this magic that depended on the level of power of a wizard. It may have been that only the most powerful wizard could implement it, or that only an equally or more powerful wizard could override it. I think that a major point was that Voldemort assumed that he was the most powerful wizard so he didn't have to worry about this, but then it turned out that the man from America was considered equal to Voldemort (or greater?) in power. I think that the plan ended up going wrong, perhaps because Voldemort brought reinforcements (it may have been giants, or tanks, or something else).
It was apparently possible to become immune to spells, particularly (I think), Avada Kedavra. Somehow the headmistress was helping the man become immune by casting it on him during their secret meetings. I don't remember how it worked, but it may have been something to do with exposing him to it in small increments and increasing each time. In any case, I believe the practices always left him very drained, and perhaps in a near-dead state, but apparently it worked. There was a one-on-one duel between him and Voldemort, where I think he ended up surviving Avada Kedavra for this reason.
What is the name of this story?