Gourgeist's signature move, Trick or Treat, has the ability to add the Ghost type to a pokemon without overriding its previous typing. Alolan Raticate is a Normal/Dark type, meaning it's immune to Ghost and Psychic attacks, but doubly weak to Fighting attacks. With Trick or Treat added, Raticate now has immunities to Normal and Fighting type attacks, its only weaknesses being Fairy and Bug. It could gain two more immunities given an Air Balloon and an immunity skill swapped onto it.
