This is basically a die roll use to simulate variance caused by minutia no one can be expected to track. This is different than Heroic Luck as this is unearned unpredicted advantage or disadvantage.
An interesting variant allows different rolls varying according to who it is affecting or circumstances. For instance each player might choose the form of their characters luck.
| Strange D20 | (strange chaotic effects) |
| Normal 3D6 | (normal) |
| Skeptics D10+5 | (tightly defined effects): |
mean(average) luck = 10.5 in all three cases
This Luck can be easily adapted to many RPGs
This form of luck is normally earned by the behaviors which your universe/gods favors. In fact a complex set of rules might be needed (although storyguide fiat may work just as well) , both to determine how this luck/karma is awarded or earned and how it may be employed.
How specifically Heroic Luck is earned varies completely from universe to universe and even from role to role within that universe. In general as a meta-game tool it may be used to reward "good" roleplaying and sticking with the genre, well defined genres are necessary for this to be used easily (If the genre is secret the SG may have to tally a characters luck secretly)
Story Guides have very big jobs it may well be in his best interest to award them.... but some players find that it ruins their sense of being "in the story" players who prefer this immersive style may wish to plan in advance what circumstances are likely to trigger their luck and allow the Story Guide to actually adjucate its use (these circumstance may take in to account more Story Guide information about whether the luck is needed than basic player controlled luck.)
Luck may be employed in ways whose effects are nearly universal, to create virtually any circumstance which is possible. Characters who are aware of their souls/spirits ability to move chance in their favor are sometimes considered Probability Manipulators/Wizards when they take an active role in this or just plain lucky when they don't.
A specialist might be "lucky" under specific circumstances and "unlucky" under other circumstances.
Kodecis Luck Page (has some interesting elements regarding use of luck in games which have death spirol combat and anime style conflict.)