My "only one" started with only one weapon on a maze...
... then I saw that the weapon could be the player's life as well!
https://itch.io/jam/gmtk-2019/rate/463767
You start in a ghost state, nothing can attack you and you can't attack anyone. When you find/get your life, then you have to sacrifice it to turn surrounding enemies into ghosts. Whenyyou do, you go back to the start, the life stays where you were and you have to find it again, but now there are ghosts that can kill kill you.