Although the damage roll is optional, it is recommended if you are using numerical damage factors. This is because the damage factors are generally fixed for the entire fight, and things tend to get stagnant. It also allows a tiny fighter to have a chance against a larger foe a satisfying result.
There are many possible ways to use a damage die roll.
One could roll a single Fudge die for a result of -1, 0, or +1. This can be added to the damage factor, or, more broadly, to the actual wound level.
For example, if a fighter inflicts 4 points of damage, that is normally a Hurt result. If a +1 on 1dF is rolled, however, that can make the result +5 (if adding to the damage factor), which brings it up to Very Hurt result.
However, a -1 wouldn’t change the wound: it would lower the result to 3, which is still a Hurt result. But if the GM is using 1dF to alter the wound level, then a -1 changes the result to a Scratch, since that’s one wound level below Hurt.
Instead of a separate damage roll, one could simply use the die rolls used to resolve the Opposed action. If the attacker wins with an even roll (-4, -2, 0, +2, +4), add one to his offensive factor. If he wins with an odd result (-3, -1, +1, +3), his offensive factor is unchanged. Do the same for the defender, except it affects his defensive factor. This system will help the defender 2525time.
Example: the defender loses the combat round, but rolls his trait level exactly (die roll of 0): he adds one to his defensive damage factor. The attacker wins with a die roll of +3: his offensive damage factor is unchanged.
The final damage number is reduced by one the defender, although losing the round, managed to dodge left as the attacker thrust a bit to the right, perhaps. He may still be wounded, but he got his vital organs out of the way of the blow.
This system could also be applied to the wound level instead of the damage factor.
A more complicated system uses a Situational roll (result from -4 to +4, not based on any trait), and adds it to the calculated damage number (the number over the wound level), as found in Determining Wound Level. Negative final damage is treated as zero damage.
The GM may wish to apply some limitations to the damage roll, to restrict too wild a result. For example:
1. If the calculated damage is positive, the damage roll cannot exceed the calculated damage. That is, if the calculated damage is +2, any damage roll of +3 or +4 is treated as +2, for a total of 4 points of damage.
2. If the calculated damage is positive, the final damage cannot be less than +1.
3. If the calculated damage is negative or zero, the final damage may be raised to a maximum of +1 by a damage roll.
First Example: The calculated damage is found to be -2 due to armor and Scale. It would take a +3 or +4 die roll to inflict a wound on the defender in this case, and then only 1 point of calculated damage: a Scratch.
Second Example: The calculated damage is +2 (a Scratch). A damage roll of +2 to +4 results in final damage of four points, since calculated damage cannot be more than doubled by a damage roll. A damage roll of +1 results in final damage of three points, while a damage roll of 0 results in two points of final damage. Any negative die roll results in one point of final damage, since a positive calculated damage cannot be reduced below one by a damage roll.
For simplicity, of course, the GM can simply ignore the limitations, and allow the damage roll to be anywhere from -4 to +4, let the chips fall where they may. . . .
Many other damage die rolls are possible these are only given as examples to the GM.