There were lot's of ways that people had predicted that the world would end. A few even had it partially correct. But how could they have predicted it would be a combination of the system apocalypse and aliens. Specifially aliens that wanted to create the equivlant of a TV show about the system apocalypse on Earth.
Arthur woke up with a headache and the option to create a character. Most people would have gone with the safe choice and selected to stay a human. Arthur suspected that wouldn't be the safe choice in his new world. Instead he decided to see what other races were available. Eventually he decided to become a dungeon core instead.
Of course being a dungeon core comes with a number of challenges. Starting with the fact that he was a giant crystal instead of having a body, managing a bunch of unintelligent minons, and most importantly the reaction of his human neighbors when they discover him.
If he can overcome these challenges he may be able to enjoy some of the benefits. Such as the fact that dungeon cores are immortal and he would eventually have an entire army of dungeon minions that would obey any of his commands. Perhaps even find some female companions that are looking for a safe place during the apocalypse.
Warning: If this fiction was a movie I'd rate it R for occasional scenes of violence, gore, nudity, and sexual content. This isn't something you would find in the young adult section. This does not mean that this would be rated NC-17 or X, if that is what you are looking for try lewd dungeon.