The hardest thing any GM has to do is come up with stuff on the fly. Especially when that stuff needs mechanical rules behind it. Fortunately, you have this Marvelous Mechanical Miscellany for Ad Hoc Adjudication and Improvisational Invention.

The problem with players is that they always want to run around and do things in your game. Things you weren’t ready for. Or ask questions you don’t have answers for. And sometimes, even your own brain will turn against you and demand you add a crazy idea to your game. So how do you change the story of your game on the fly?

What do you do when the rules fail? Well, you’re the GM, so you’d better do something! The game is waiting! You need to make a call! Hurry up and make something up.