Rowan Tree and Red Thread

This is primarily aimed at the players in my Elizabethan Superspies role-playing game. We're using a variant of the HeroQuest rules, thought up by Alex Ferguson (aka alaimacerc). I've wondered about going a step further and making it entirely 'roll and add' rather than the 'roll under' system used in the published rules and Alex's variant.

Conversion

You have a rating in each ability on your character sheet. These ratings can run from 1 whatever, the higher the better. To convert current ratings multiply the number of masteries by 10 and add the target number you currently have. E.g. You have ‘Impressive Whining’ at 5M. That’s 10 x 1 mastery plus 5 = 15. If we were still using the basic rules each mastery would be worth 20 points.

Resolution

Roll d12 and add your ability and compare with the total rolled by the opponent, or natural resistance (also d12 + ability). If you roll an ‘11’, roll again and add 10 to the result. Repeat as necessary. If you roll a ‘12’, roll again and subtract 10 from the result. Repeat as necessary.

The higher roll wins. Beat the opposition by ≤ 10 points, marginal victory; ≤ 20 points, minor victory; ≤ 30 points, major victory; greater than 30 points, complete victory.

Improving abilities is as before. I think we're using something like: 1 hero point to increase an ability by 1 point. 2 hero points to add a new sub-power to one of your powers, and 6 hero points to add a completely new power.