Let’s begin with three principals:

We all make mistakes.

We’re playing to have fun.

The rules are tools that help us have fun.

These are all pretty basic. So when someone makes a mistake regarding the rules (like Nadav did in this week’s page – he forgot about an additional negative modifier on Rotem’s roll, check the post for details), here’s how these principles come into effect.

First, did anyone notice?

If no one noticed, it doesn’t matter. We follow the rules as means to an end, so making sure we’re always “correct” just isn’t a priority. No one should try to always keep us straight, for straightness sake.

Second, if someone noticed, do they care?

If the person or people who noticed have some opinion about the mistake, proceed to step 3. Otherwise, who cares? No, literally, is there someone who does care? If you yourself don’t care, but you know that someone else will get really bummed when they realise (maybe never, but maybe in a few minutes) that someone made a mistake that they feel could have affected the game, then someone does care, even if it’s not you. Consider making the mistake known for everyone.

Third, if someone cares, will correcting the mistake derail us too much?

The rules are tools to have fun. If we destroy some of the fun just to make sure the rules are being followed, we’re probably making a bigger mistake, so let’s first make sure that correcting the rules mistake will help us have more fun. Here are a few possibilities:

Will correcting the mistake require a time bomb?

When you “time bomb”, you all agree to change the canonical past in a way that takes the corrected mistake into account. The bigger the change, and the further into the past it is, the bigger the effect it will have – and that “effect” is usually “everyone grumping while having to re-do their last few actions, wondering if it’s worth it”. That sucks and takes you right out of the immersion. Small changes, however, can be made with little difficulty, and some of them can be very fun-enabling.

Example: The orc just hit me for tons of damage! I need to— wait, we forgot I barred the door before running away, it should have stopped the orc for a moment! This is a great opportunity for added tension – let’s roll Strength for the orc, to see if she manages to burst through the door. If she makes it, then the rest of her turn will continue as it already had. If she fails, then she never managed to get through the door, and so you didn’t get hurt! The player feels as if it’s a second chance not to get hit; the tension of the original attack roll is replayed, in a sense. Furthermore, ignoring the fact he barred the door is ignoring his agency and his effect on the world and the story – something you should always avoid anyway.

Another example: I just remembered the spell I cast three rounds ago also make the orcs afraid of me. Well, since then one of them attacked us twice, another grabbed a prisoner, a third poisoned the bard, and the monk had an amazing grapple moment with the fourth. Too much interesting stuff happened… So we’ll just say that part of the spell didn’t work this time. This is a great opportunity to add something interesting to the story: Why didn’t it work? Are the orcs too infused with bloodlust? Did you fumble the last part of the spell because you were too distracted by the prisoners? Don’t let the player feel as if something he deserves to have – like a spell effect – is simply wasted. Make it still count, as a source of additional story details.

Will correcting the mistake affect anything interesting?

Let’s say Nadav realises his mistake a few moments after Rotem’s roll. If he calls for a mini time bomb (“Oy, oops! I forgot about this modifier), he can either add the mod and continue on (“But Nadav, that’s unfair! I wouldn’t have rolled if I’ve known it’s THAT bad”), or he can explain the full rules, ignore the original roll, and again present the option for rolling. The latter is better, but better yet is not doing anything.

If she fails – which is highly likely – nothing interesting happens. In a way, it’s better for the story that she made the roll, even though she shouldn’t have, by the book. Does that mean we should make every roll a success? No, because while “success pushes us further” is indeed a good rule of thumb, a good GM should always consider the circumstances. Lili failed her roll just a moment ago, and it helped the atmosphere and the story. But now that the party is sure something is off, they should succeed in their effort to gain at least some information – they should feel as if they can learn something, they can advance in the mystery. (It’s even better that while Muna made her check, she still doesn’t share the information with the group because of her being easily distracted – the players feel the world is fair and manageable, the problem is with themselves!)

Anyway, a few minutes after the fact, Nadav should make it explicit that there was a mistake, and point out the correct rules, so that everyone is clear on them. This is very important – the rules must remain consistent so they’ll be fair. Nadav, as the GM, has the right to change them whenever it helps the story, but the players should always have a clear understanding of the rules. This power has a huge penalty, it will still be there next time Rotem wants to use it, and so she must be aware of it, so she’ll be able to take this into consideration and make an informed choice.

Does it matter who made the mistake, the GM or a player? A bit, but this article is long enough as it is; feel free to offer you suggestions on the matter in the comments. I also encourage you to check this thread, in which you guys started helping us develop political organisations in the world of Crystal Heart.