I like the compromise above: if you take advantage of a weakness, you have to narrate a flashback (or something) explaining how you learned. Solid die rolls (or skill levels) are very helpful at getting everyone on the same page.

One great way to encourage sticking to IC knowledge is to reward players for not using their special knowledge. Bennies, an extra action point, or immediate willpower recover are all great ways to say “atta boy”. If you combine that with unwinder’s solution: it’s vulnerable to one metal, not necessarily the one printed in the book– you can keep people on their toes and reward the discover in game.

If the discovery of the special metal that can be used to combat these creatures is a major part of the plot, then I see two solutions. A) The enemy has mutated an immunity to that metal, so they have to discover a new way of combating them. B) Create an all new baddy (but use the same stats and behaviours of the original creature), they’re not werewolves, they’re the dreaded Wyzers, who change into animals on full moons, but there’s rumors that they have a weakness to something!

In a fantasy world (most likely) neither case is true. Consider how little one knew 50 years ago, 100 years ago, 500 years ago – compared to now. The average person didn’t know what was going on in the next town. Only the most educated had a wider idea, and even they did not have widespread knowledge. The discoveries in one place my not get around the world for a century.

Common knowledge in a medieval fantasy world is pretty slim. I never let my PCs get away with that. I have a problematic PC that tries to incorporate his knowledge of metal alloys in trying to create new weapons and armor. I constantly remind him, that he knows it, but his character has no idea. Even if he were a dwarf, he would be more knowledgeable than the average character, but he wouldn’t have the player’s knowledge regarding such technology.

Perhaps she heard stories as a child. From whom? Boom–the GM has a hook for a future story. Maybe the trolls are pissed that some retired adventurer is revealing their weaknesses to children in the characters hometown, and so attack the town, and your characters have to intervene. Or perhaps the character was in the militia and defended a town against troll marauders. The GM can then reason that the trolls know as much about the character as the character does about the trolls–perhaps the trolls know the militia tactics well and get a numeric advantage against the character.

Of course, the former example is fun and story-driven, but the latter example runs the risk of not being “fair.” So, for me, the latter example is where the “knowledge check” roll comes in. The GM can invite the player to explain how he could know the information, then make a roll. If he succeeds, he knows and can act on the information. If he fails, he knows and can act on the information, _and_ some penalty arises out of the circumstances of the backstory.

This can work the other way, too… if the GM sees a player metagaming (attacking the troll with fire), the GM can call for a knowledge check in the above manner. This way, if a player chooses to act on something, he doesn’t have to later pretend to forget about it–he just has to be willing to live with the consequences.

And, let’s face it, the consequences are generally what makes the game fun.

You then have two options when rolling it: You can either create the fiction you want (“There’s an abandoned fortress over that ridge where we can rest up.” – Fortress-wise, or Ruins-wise, etc) or you can seek information from the GM, as per D&D and other systems.

The first option is what makes it awesome. The GM doesn’t have any specific plans for that town up ahead? Well, one of your players might. “The town’s been crawling with religious zealots recently and there’s no end of tension between them and the townsfolk.” (Converts-wise, Faithful-wise, Rumour-wise, etc) Sweet! Now there’s something there, and whaddaya know… it matters to at least one player.

One could introduce the same sort of idea (the other side of the Knowledge check “coin,” in other words) to D&D pretty easily.

I really like the “Hash It Out Beforehand Then Roleplay” part, John. I think that’s the best option for just about any system.

Because it’s my campaign, and I say it’s bronze.