Myth - a traditional or legendary story, usually concerning some being or hero or event, with or without a determinable basis of fact or a natural explanation, especially one that is concerned with deities or demigods and explains some practice, rite, or phenomenon of nature.
It's certainly debatable, but the idea of a myth always being untrue has long since fallen out of style. The word's meaning has vastly changed over the years, and I see no real reason to argue with the current usage. It's simple, and conveys the idea easily enough that anyone you are discussing it with will know what you mean.
It reuses a couple names and otherwise completely ignores the source material. If Paradise Lost counts as Christian Mythology, then Final Fantasy counts as Hindu mythology just for using the name "Shiva", and counts as an extension of Kabbalah for using "Sephiroth".




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