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An interesting observation, but highly doctored to suit the argument you are trying desperately to prove. There is the issue that you are generalizing the skeleton of the plot so much that you are of course going to hit similarities. Also the saying "It's all been done.." comes into mind. But other than that, the most glaring issue is the in-correctness of your information.

Durza is no one's father. He is a shade. Period. A man who chose to control spirits with dark magic.

Brom actually dies long after Arya has been rescued and this part of your argument relies on the movie's warped version of the storyline.

Brom is Eragons father, not Durza, and this is not discovered until Brisingr.

Murtagh does not leave, he is kidnapped by the Twins, who betray the Varden and were actually working as spies for Galbortix the whole time. Murtagh is then forced to swear allegiance to Galbortix as Glabortix discovers his true name in the old language, which allows him to control him.

The city/outpost argument has the biggest hole. Number one, it's a dwarf city, deep in the mountains, and it's not even located within the empires borders, but rather far from them. In the books there are 4 main entities/empires, the Empire, The Du Weldenvarden ancient forest, controlled by the elves, The beor mountains, controlled by the dwarves and the many houses of them, and Surda, an empire free from Galbortixes rule. The Varden are hiding from Galbortix and are hosted by the dwarves.

I haven't read Eragon in a few years, and only once to begin with. But still, the plot is almost exactly the same.

But, yes, I have seen my mistakes. Morzan is Murtagh's father, and he and Eragon share the same mother. I heard most of the spoilers for the third book, but I was not told that Brom was actually Eragon's father.

With Brom's death, I was again confused, but you are wrong as well (at least according the half-reliable, wikipedia. Yes I'm at the book, not the movie right now). Arya was rescued after his death.

Murtagh technically does leave, but not by his own choice. Wasn't there a dude in Star Wars 5 that betrayed them to Darth Vader at one point, then turned good again? I'm guessing that's gonna happen to Murtagh.

Once again, the city was confused with the Elf forest to the northeast (it is that, right?) but, still, don't they start a war with Galboratrix later on?