The goal of any good story teller, be he a game master, a writer or a director is to create tension. Tension can be created by many things but in gaming, it boils down to the perceived chance of failure. The word “perceived” is very important because if a player knows they’re going to win, there’s no tension, regardless of how true that statement is.
If a player is 100% sure he’ll win there is no tension. It doesn’t matter if he already swallowed the poison and will die in 2 hours. If he doesn’t know about the poison he’ll just feel cheated by the game master when she smugly announces the players fate.
On the other hand, if there is no chance of failure but the player doesn’t realize this, via deus ex machina, the player still experiences tension. For example, the player learns they may have been poisoned and might die in 2 hours. The game master knows their fine but the player experiences tons of tension as she desperately tries to find an antidote. The downside of this technique is is that if used too frequently the player expects it and you wind up with a player who is 100% sure he’ll win.
With Flex, I’ve been trying to balance the system to the point where using the assumed difficulty (players with X character points vs npcs with X character points) there is very little chance of complete failure and yet, there is still tension in combat. Ideally, I’d like to see one player out of three be defeated in every combat, baring excellent teamwork. Given that defeat usually doesn’t mean character death in Flex. I think this is a pretty good goal.