Pie Factory Designer
Co-founder of Nevermore Games. Follow me on Twitter @bryanfischer
My first assumption was that it's for determining the starting player, since there isn't a specific rule for that in the rulebook.
Actually there is a rule for starting player in the rulebook, it's the player who speaks the most Latin. But really, you can determine it any way you want
As for the die...
The die is just a little something extra from Game Salute to all backers of the game. It doesn't have any in-game use, but can be used to determine first player if you so wish. Enjoy the custom made die!