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Prolouge: Mark of Mastery exam
No ones POV
Once upon a time, there were two great Keyblade wielders, one by the name of Eraqus and one by the name of Xehanort. They were both young, strong, and full of spirit. They were also best friends, but their mark of mastery exam will change their lives forever. The last test was to spar with one another, they have spared many times before, but this time it was the thing that decided if they were going to be Keyblade masters or not. It is the final to see if they can fight against the darkness or not. They were both nervous, but Xehanort was so nervous that the darkness that he has suppressed inside found its way out during the test. This darkness that was not suppressed was the thing that made him fail the test. He brushed it off his shoulders for the time being, but he was still upset that he didn't pass the test.
After failing the test, he decided to take a new approach to winning the title of Master Keyblade Wielder. Instead of suppressing the darkness within him, he decided to come to terms with it. After a while he knew how to keep his darkness in check, but his ambitions made him more dark than light. Nobody noticed, though.
At the next Mark of mastery exam, he passed with flying colors. After he became a Keyblade Master, Xehanort started to learn about the history of Keyblade wielders. The thing that interested him the most was the Keyblade War. He started to have new ambitions, to create the next Keyblade War and to forge the X-blade. This was easier said than done, though. He needed a pure light and a pure darkness to fight to forge the X-blade, which unlocked Kingdom Hearts.
A young new Keyblade wielder named Ventus started training about the same time Xehanort started his ambitions. Xehanort decided to take the young Keyblade wielder under his wing and tried to teach him to fuel the darkness within him. Ventus refused to do it and got hurt in the process. After that, he took all of the darkness inside of young Ventus out of him and gave him to his old friend Eraqus to train while he trained Ventus' evil doppleganger, Vanitas.