You have served your god well. You have smitten the enemy, converted the infidel and kept the faith. All your life you have been told that the afterlife will be an eternal party, a never ending revelry in which your slain foes will be servants. So when you and your comrades finally slew the Spider-demon King, bringing down the rood of his temple on your own heads in the process, you figured you'd gotten a decent deal out of life. Unfortunately, the afterlife is not what you expected. It turns out the party's full, and you're not invited. The enemy is at the gates, and your god needs more warriors to throw into the fray. Sure you've got an army of goblins and heathens at your beck and call, but just try to get served at a pub in the afterlife when you've got a 12 foot tall spider demon looking over your shoulder.
This could be a one-shot RPG, a board game, or even a goofy "cheapass games" style board game.