D&D General Being a PC in an adventure you've already GMed

[Baldurs_Underdark]

So, everyone here is thinking of the same: If you know the whole campaign inside out, your PC might e.g. be able to take a central role in the game, take big decisions, anticipate events or find hidden loot before others.

Risk = Chance x Effect

Next questions are therefore, what is the chance and what's the effect?

The effect might be the easiest, because you know your friends. If nobody takes the game very serious, and it's just an excuse to have a beer together, then maybe it's alright. But if a friend might get a grudge or people become jealous and annoyed, then this is a possible game-breaking effect.

What are the chances of these problems occurring? If your DM adds enough homebrew stuff, you may be just as clueless as the rest. But if the DM sticks closely to the pre-written adventure and you cannot play dumb, then you have the knowledge to give yourself an advantage. Then the only question left is whether you can play dumb?

Personally, I would not play a campaign that I already know. I cannot play dumb. I'd tell the DM that I know the story, and ask the DM to mix up some things to ensure that I don't know what happens. If that is not possible, I would step out.

 

[BrokenTwin]

It's only happened to me once, and it honestly did not go well, though it had little to do with me knowing the adventure and more the GM being insecure about it. I had been taking extensive notes about what the GM said during the game (to avoid bringing up something that hadn't yet been revealed), and at one point we had entered a small-ish room in a dungeon where there was some guards playing dice around a table and a door on the far side. After combat I said I wanted to go take a look at the door, and he flipped out about me knowing a door was there. I responded that he had already told us the door was there, and given that it wasn't a secret/hidden door, there's no way our characters wouldn't have seen it, given that... you know, it's a door, directly across from where we entered. Would have been impossible NOT to see it.
Next session he made some large changes to the layout (which I'm perfectly fine with), but explicitly mentioned that he did it so "certain people" would stop cheating. Left the game and didn't look back.