Mano a Mano:Success Rolls

Success Rolls

Rolls and Modifiers

Some actions are always successful and some are never successful, but many actions have a random chance of success. When rolling for the success of an action, roll a twenty-sided die (d20) and add success modifiers to the result. If the total is greater than the difficulty of the action plus difficulty modifiers, then the action is successful. The action is also automatically successful if the die roll is 20 before adding success modifiers.

If you do not have a d20, you can roll a ten-sided die (d10) and double the result (d10 × 2). If you roll a 1 the doubled result is 2, if you roll a 2 the doubled result is 4, if you roll a 3 the doubled result is 6, and so on. Most d10 are numbered 0 to 9, but the 0 represents 1, so if you roll a 0, the doubled result is 20. The chance of getting 20 this way is twice as likely, so you can ignore the automatic success rule, or make a second d10 roll, but don't double the result. If the second roll is more than 5 then the action is automatically successful.

If you do not have a d10 or a d20 you can use a six-sided, eight-sided or twelve-sided die (d6, d8 or d12). Subtract 1 from the result and then double the value if you use a d12, triple the value if you use a d8, and multiply the result by 4 if you use a d6. (Instead of subtracting 1 it may be simpler to count the highest number on the die as 0.) If the result is 20 or more, you can either ignore the automatic success rule, or make a second roll with the same die. If the second roll is more than 8 on a d12, more than 5 on a d8, or more than 4 on a d6 the action is automatically successful.

first roll	automatic success (if the first roll is at least 20)
d20	always automatically successful
d10 × 2	roll 6, 7, 8, 9 or 0 (10) on a d10
(d6 - 1) × 4	roll 5 or 6 on a d6
(d8 - 1) × 3	roll 6, 7 or 8 on a d8
(d12 - 1) × 2	roll 9, 10, 11 or 12 on a d12

Difficulty

difficulty	description
5	Anyone will usually succeed
10	Experts usually succeed
15	Difficult even for experts
20	Nearly impossible without training
25	Often impossible even for experts

Difficulty values are often determined by adding 10 to a modifier such as a character's ability level. This can be used to resolve contests between character's using different abilities or the same ability against each other. For example, suppose two characters are having a contest, and both have the same ability level. Adding that level to a die roll for one character and adding that level to a difficulty of 10 for the other character gives both characters a 50% chance of winning the contest.

If a contest can be tied, do two success rolls with each character taking turns adding their modifier to the roll or a difficulty of 10. One character can succeed while the other fails or the result can be tied two ways: both characters can succeed or both characters can fail. If it is not possible for both to succeed, then both characters fail when either type of tie occurs. If it is not possible for both to fail, then both character's succeed when either type of tie occurs.

Circumstance Modifiers

Environment and hastiness can effect the difficulty of an action. Add 2 to the difficulty modifiers for unfavorable circumstances. Add 4 to the difficulty modifiers for hostile conditions. Modifiers for unfavorable circumstances and hostile conditions are not added to other modifiers for unfavorable circumstances or hostile conditions. When more than one of these modifiers apply, use the modifier which increases the difficulty the most. If multiple unfavorable circumstances compound each other, treat the combination as hostile conditions by adding 4 to the difficulty instead of 2.

Add 2 to the success modifiers for favorable circumstances, or add 4 to the success modifiers for very favorable circumstances. Modifiers for favorable or very favorable circumstances are not added to other modifiers for favorable or very favorable circumstances. When more than one of these modifiers apply, use the best one. If a combination of favorable circumstances is much better than the individual circumstances, treat the combination as a single very favorable circumstance by adding 4 to the success modifiers instead of 2.