One of the best ways to introduce new rules or ideas and to run a narrative scenario is with the help of a Games Master. A Games Master (or GM for short) is an optional third player who takes a role somewhere between that of a narrator and of an impartial arbitrator of the rules, who presides over and runs a particular battle. The GM helps the players by setting up the scenario and interpreting and amending – or even making up – the rules as needed.