>>29587143there's a guide somewhere online that'll tell you how pokemon react based on nature.
basically pokemon have two battle stances. i'm fuzzy on the numbers, but i believe it's the same trigger activation as blaze/overgrowth which was something like 33% max hp.
your pokemon will behave a certain way until it reaches that threshold. once it does reach it, it takes a different approach to battling.
for example: a pokemon with X nature will be a pacifist until it hits 33% max hp, at which point it will become aggressive.
there's a little girl in one of the buildings at the frontier which will assess your pokemon and tell you how they will behave, but it will be vague and in kids terms using words like "ouchies".
the battle palace is about knowing your pokemon's nature and teaching it the right moves that it will work best with. basically, you need to do 110% studying to create a good team.
good luck. i hope this helped!