>>55117745>Nature changing is postgame (allegedly)If you talk to the scientist in Tehl Town and complete his quest of showing him all Deerling forms he unlocks nature changing for you! The last Deerling you need is in Route 12 right before Dehara City. First change is free but the rest cost $50,000...
Also pro-tip, if you're planning more runs (especially Insane which is brutal) I HIGHLY recommend making a New Game+ Save file off this bros save:
https://www.reddit.com/r/PokemonUnbound/comments/x5thfx/presenting_legit_living_shiny_dex_fully_evolved/It comes with the fully-upgraded Stat Scanner that you can use to alter nearly everything about a mon with ease.
You can also pull any 6 mons fron the box into your team so you can start with any shiny team of 6 you want! This save file was a lifesaver for my Insane run.