The idea is that players are secretly linked: one as a regular being, one as their guardian angel.
But you don’t know that. You need to figure that out through which cards you play.
How? Your “role” is assigned through the cards you have in your hand. => Would need to find a way to ensure all roles are distributed, and nobody has 0 or 2+ roles.
Objective? You win together. The angel must prevent bad stuff from happening to their partner, so they stay alive / score the most points when all cards have been played.