So what does 13 deliver in-game? You choose – it operates as a wildcard, which can be linked to any number of possible outcomes. Ideally, the chosen outcome will not so much interrupt the flow of play as become part of the flow of play. This calls for a light touch when selecting a default. The lightest of these is to forget about 13 and stay with the standard 1 and 20 outcomes found in D&D, S&W, OSRIC, Labyrinth Lord, . . .
Stick or Twist
However, Corruption, Renegade, and all the others listed above, can easily introduce a 1, 13, 20 system where 13 acts as an option to re-roll:
- When the target roll is known and a 13 is successful a player just has to avoid the temptation to go for a 20 – which wouldn’t be a smart move for a saving throw.
- When the target roll is unknown a player is tempted by the unknown, the chance of another shot at rolling a 20 and the possibility that 13 is enough to get the job done.
If players start dithering just nudge the default 13 ever so slightly by adding that the player has a count of 13 to decide or the roll stands.
13 As A Wildcard
Homebrewing/ customizing/ taking ownership of your campaign can also benefit by selecting a group, campaign and/ or game default. For instance, if the optional Corruption attribute is being used adding to the basic re-roll by charging PCs a point of Corruption each time they opt for a re-roll has two effects. Firstly, it reduces use of re-rolls and, secondly, it encourages a gradual descent into evil and corruption.
If a group really does want to put more icing on the cake combination effects can give 13 even more impact, while clearly still only occurring occasionally. For example, a descent into corruption re-roll can also be linked to triggering episodes of the corrupt behaviours that sometimes overwhelm the very corrupt. For lawful parties this has more effect on evil opponents – who keep losing it. However, for PCs on the cusp between good and evil a sudden lurch into chaotic mode could be wildly embarrassing or even seal their fate.
Other options, which could be tied to a mechanic, a campaign or a theme such as Corruption’s twist of evil might include awarding a stock of luck or hero points to PCs who make a successful second roll.