This allows you to roll for who will win in combat. As this is 'final' it should be the last roll to decide the overall victor. All parties should roll if it's requested (though we'd still rather you just RP'd out your whole combat). Some basic rules: 1) If it's one vs one then the two roles are directly against each other. Higher roll wins, difference between the roles is a good indicator for how close it is. 2) If it's one vs many then the aggregate total of the many goes against the single roll of the one. 3) If it's many vs many than the aggregate total of each group goes against the aggregate total of the other group.
Basically, you may be uber, but you can't take on the world by yourself.
Technical Note: +final combines all of your styles together, as well as your secondary stats, to come up with the number with a bit of randomness thrown in at the end.