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Augments, customizing Pokemon in completely new ways. , can only be done once per Pokemon. Cannot be done to Pokemon with BST over 580. Cannot have two Augments on a Pokemon at the same time.
Augment Y - Switch two of a Pokemon's base stats at a time. You can switch a Flareon's base Speed with its Special Defense, so it now has 110 Speed and 65 Special Defense.
Augment X - Boost a low stat, the lower it is, the better a boost it gets. Higher stats are less affected. I don't even formula but you might end up getting a Wigglytuff that can tank physical hits better now.
Other stuff:
Groudon and Kyogre get the old Drought/Drizzle, Ninetales and Politoed get a weaker version that lasts 5 turns after they switch out, unless they hold wet/dry rock item, then it will last for 10 turns. Snow Warning and Sandstream also get the same treatment as weaker Drought/Drizzle.
IV system replaced with a new system with more control and trade-off, it is easier to get the IVs you want but it is impossible to get perfect IVs in all stats.
Pokemon can have two abilities now, one is static and always the same, the second can be customized, from a list of abilities a single Pokemon can learn. Example: Flygon's primary ability is Levitate, its secondary can be Sand Stream or Tinted Lens.
A second set of shinies.
Hats. Completely cosmetic.
