Boons and Banes represent a nice little bound mechanic in Draw Steel. I did a little Google Sheets to figure out some of the math. There is already a bunch of talk out there about the game’s math, like this post on Reddit, which goes into way more detail than I have here.
An unmodified roll would result in a table something like this:

While a single boon would affect the table as such:

and a single bane like this:

Things get a little more interesting with Double Boons and Banes.
Shifting tier results makes the charts look like this for Double Boons:

And like this for Double Banes:

Also interestingly enough. Your chance for a critical is always 3%. That doesn’t change with any Boons, Banes or other bonuses/penalties.
Hopefully someone finds this information useful. I mean the single boon table also applies to a Power Roll with a +2 modifier and the single bane table is a direct representation of a -2 Power Roll modifier.
Yes I did my tables kind of strange and probably screwed the math up a bit. I’m defiantly not a spreadsheet professional.