#totem pokemon

Totem Pokemon are just

Alolan Alpha Pokemon

Think about it- a large pokemon that oversees an area, and gets a burst in power not seen in others of the species.

Possibly Hisuian Alpha Pokemon were brought to Alola, or it was a divergent evolution scenario. Perhaps having a few larger, stronger specimens to control an area was advantageous, and these traits were passed down the generations of Pokemon. And the Alolan people began to revere their “Totem” pokemon, like how they do in Hisui with their “Lords and Ladies”

This would explain how the player in USUM is able to get their own Totem Pokemon. And why Totem pokemon can change when new trial captains are chosen, matching the new trial types. And how Totems can be replaced if the previous one is lost.

Gosh I put too much thought into this theory but

Oh my god

It makes so much sense