This mod came from steam user Yoshiko, and it features runs with silly conditions (only pawns, only bishops, you only have cannonballs, you only have plague, etc.). I'm going to try out some of the more interesting ones. I've played this mod before shotgun king had the steam workshop enabled, and it's been changed since, so I might as well check it out again.
Shotgun King: the Final Checkmate
store.steampowered.com/app/19...