Yamask's evolution to Cohagrigus.
Lemme sum it up for you. When you die, you become a ghost pokemon. It makes sense (albeit in a morbid kind of way). But when you hit a certain peak of your afterlife you turn into a FRIGGING SOLID GOLD COFFIN THAT EATS ANYTHING IT CAN.
It's terrifying, comes out of nowhere, and the implications? EVERYWHERE.