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From the information you provided, I would say making it a prologue would be fine. Of course, I don't recommend info-dumping in the prologue, saying, "The world balanced on the backs of elephants w...
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#3: Attribution notice added
Source: https://writers.stackexchange.com/a/30421 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
From the information you provided, I would say making it a prologue would be fine. Of course, I don't recommend info-dumping in the prologue, saying, "The world balanced on the backs of elephants with a big-ass turtle beneath it..." yada yada yada. But this seems that it belongs as a prologue. A lot of readers like prologues, a lot of readers don't like prologues. Go by your gut and write the prologue. You can only really know if it should stay or go is when you self-edit, send your manuscript to an editor, or get one of your friends to check it out. At least get the rest of the story out of the way before worrying too much over the prologue.