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I'd love to be able to play Inverse Battles on Pokemon Showdown. It's one of my favorite things from back in XY, and I'd love to see it in action for Gen 8, Nat Dex, etc.
While there aren't any ladders for this (other than randbats mayhem), you can challenge someone to an inverse battle in any format by adding the `Inverse Mod` to it. For example: /challenge <user>, gen8ou @@@ Inverse Mod