Hi there,
I'm converting my Werewolf: the Forsaken game to Solar System and I am just ironing out some details. If anyone is interested, I can post what I have converted here.
However, my question for this post is whether there is a limit on the amount of penalty dice that can be assigned to a check. It would seem that the most penalty dice you can get for circumstantial penalties are two, but is that the intended upper limit for penalty dice? If so, what is the reason for that?
By the way, I think the Solar System is an awesome system and I would like to see some fully-fleshed out settings that utilise its mechanics.
I'm in the process of re-writing Shadow of Yesterday, so if everything goes well, we'll have such a setting this year. Others have their own projects as well.
As for penalty dice, there is no limit. The two-dice limit is solely for the Story Guide dice which he can assign at will. You could even mess around with that limit if your genre needs it, too.
In general, remember when creating new crunch that penalty dice are somewhat more valuable in most settings than bonus dice simply because they are less common. When there are both types of dice in one check, the less common type has more impact on the overall result on a per-die basis than the other type due to how the dice probabilities play out. For this reason I tend to make penalty dice boosters and such slightly more exceptional/expensive than the equivalent bonus dice booster.
Note that there is a diminishing return of adding more penalty dice, and as such a hard limit of penalty dice is not needed.
That said, you can get penalty dice for Harm (up to 5 before you collapse anyway if you play it the way I do), circumstantial modifiers (up to 2, just as Eero described) and probably due to some Effects and Secrets). I think I've never seen more than 3 penalty dice after accounting for bonus dice eliminating penalty dice in actual play, though.
Thanks Eero and Harald for the fast response. I had the feeling that there wasn't a limit on penalty dice, but I wasn't sure.