Rolling the Dice (or Not)

Know When Not to Roll
Contests in Isekai are frequently resolved by rolling dice. In many situations, however, the GM should avoid rolling dice.


 * Don't Roll Unless Failure is Interesting
 * Don't Roll Dice if You Can Role-Play

If failure is not an opportunity for interesting play, rule the action successful without a roll, or make a roll only for the cost of success. If an action can be resolved by interaction with an NPC, role-play the interaction to determine its result.

Die-Rolling Mechanics
Each side rolls a pool of ten-sided dice. The pool with the highest single die wins. Compare the rolls to determine the winner's number of Victories, which equal the greater of:

The winner’s highest die minus the loser’s highest die, or The number of the winner’s dice which are higher than the loser’s highest die (to a maximum of 9). In case of a tie, remove both tied dice and consider the remaining dice; repeat as necessary. If ignoring ties leaves the loser with no dice, the winner gets only 1 Victory.

Variations on the Die Roll The simple mechanic above can in theory be adapted to any situation. But while it works well for simple situations such as a tug of war, in more complex contests it requires more time than is fun for most players. Accordingly, a number of variations are used to speed up play.

3 Types of Die Rolls

Action-Rolls are for making an attack or taking any other action. Defense-Rolls are for resisting an attack or other action. Second-Rolls add dice to a die pool. A Second-Roll cannot change who wins, but it can change the number of Victories. Ignore any Second-Roll which reduces the rolling character’s number of Victories. Quick Rolls

Quick rolls directly compare Action Rolls to determine winners and victories. These are mostly used for contests between NPCs.

Advantage and Disadvantage

Dis/Advantage allows modification of an already-rolled result, and modification of some but not all uses of a roll. It is also a handy modifier for ad-hoc rulings.

With Advantage you count your highest die twice; with Disadvantage you ignore your highest die. Advantage and Disadvantage do not stack, but some situations may impose Double Disadvantage (ignore highest 2 dice).

Initiative Advantage doubles your high die only for the purpose of determining who goes first. Hit Advantage doubles your high die only for the purpose of determining who wins the contest. Damage Advantage doubles your high die only for the purpose of determining how many Victories the winner achieves. Damage Disadvantage can never reduce a successful hit to less than 1 Victory. Threshold

Thresholds are pre-rolled values which can substitute for a normal die roll. The roll result is the median value for the listed dice.

3 dice	6 dice	9 dice	12 dice	15 dice	18 dice 8 8 4 1 1	9 9 8 5 3	10 8 8 5 3	10 9 8 8 7	10 9 9 9 8	10 10 9 7 7 21 dice	24 dice	27 dice	30 dice	33 dice	36 dice 10 10 9 9 8	10 10 9 9 9	10 10 10 9 7	10 10 10 9 9	10 10 10 9 9 9 9	10 10 10 9 9 9 9 9 9 9 Take-Away Dice

Some actions can act on several targets, or in several areas, or over several rounds. A roll is made normally for the first target, round, or area. Subsequent targets/rounds/areas use the same roll with the highest die removed after each target or round. Effect ends when highest remaining die < 9. Take-away area effects normally use a 15’ diameter center surrounded by 5’ wide rings.

Slow Rolls

Slow Rolls are used to generate a random duration for some effect. When a random duration needs to be rolled, each roll should be delayed until needed. For example, if some effect is to last for 3d6 rounds then you roll 1d6. Roll the second die when the round count reaches the first dies result. Roll the third die when the round count reaches the sum of the first 2 dice. This simulates the character's uncertainty about the length of the effect.

Magic Numbers

Use Magic Numbers to simulate unpredictability. The Magic Number is a second random value derived from the same die roll by grouping the dice by the face (eg. 8) that they are showing and determining whether the count of dice in each group is even or odd. If the 10s group is even, the Magic Number is the count of consecutive even groups beginning with 10. If the 10s group is odd, the Magic Number is the negative of the count of consecutive odd groups beginning with 10. (Eg. a roll of 10 10 9 9 9 9 7 7 7 6 ... results in a Magic Number of +3 because 10s, 9s and 8s are even, but 7s are not.)

The Magic Number is always available for use if you need a quick random value, but generally Magic Numbers between -3 and +3 are ignored.

PRIVATE PART (GM)

Sometimes rolls are also categorized as Aggressive or Reactive. Usually Action-Rolls are Aggressive and Defense-Rolls are Reactive, but Perception is always Aggressive and Stealth is always Reactive. Other exceptions exist.

Why is this here? Second-Rolls allow you to modify results (eg. damage) without changing probability of success. Aggressive and Reactive are used in some spell effects.

The Basic Mechanic: Resolving Contests with Die Rolls
Everything is Measured in Dice. All game values are measured not in levels or in points, but in dice. Most often a quality's number of dice is what that quality adds to Bob's die pool, but it can also designate a threshold or be used in other ways.

Don't Roll Dice if You Can Role-Play. Physical contests will often require a roll, but most social interactions can be resolved with little or no die rolling. If a die roll is needed, assign numbers of dice to the PC based on his roleplaying, and to the NPC based on your knowledge of his character.

Don't Roll Unless Failure is Interesting. If failure would be boring, don't call for a die roll. Just because a pattern exists for a roll doesn't mean you should use it. For example, you might instead assume success, and roll once to see how long that success takes.

If You Really Have To Roll... Each side rolls a pool of ten-sided dice. The pool with the highest single die wins. Compare the rolls to determine the winner's number of Victories, which equal the greater of: In case of a tie, remove both tied dice and consider the remaining dice; repeat as necessary. If ignoring ties leaves the loser with no dice, the winner gets only 1 Victory.
 * The winner’s highest die minus the loser’s highest die, or
 * The number of the winner’s dice which are higher than the loser’s highest die (to a maximum of 9).

Variations on the Die Roll
The basic mechanic is theoretically adaptable to all situations, which allows players to try anything that they can imagine. However, for routine situation the basic mechanic can require more time than is fun. The additional mechanics below make play faster.

Definitions: Action-Rolls, Defense-Rolls, and Second-Rolls
 * Action Rolls are for making an attack or taking any other action.
 * Defense Rolls are for resisting an attack or other action.
 * Second Rolls add dice to a die pool. A Second Roll cannot change who wins, but it can change the number of Victories. Ignore any Second Roll which reduces the rolling character’s number of Victories. Second Rolls should be used sparingly, as they prolong combat.

Thresholds
In some cases Bob's Action Roll must exceed a certain Threshold for his action to succeed. If the Threshold is not met the action fails and there is no need for a defense roll. In other cases the Threshold is the only defense which Bob must overcome. Numbers of dice not on this chart should be rounded to the nearest value which is on the chart. In the rare case where the number of victories matters and the die roll ties with all the values listed below, consider the next value to be a 1.

Thresholds can be used instead of die rolls to save time, and can represent additional barriers to success such as range or local magic resistance. They are also useful for obstacles of fixed difficulty, such as climbing a wall, and for "passive" perception, ie. being noticed by someone who is not actively looking.

Advantage and Disadvantage
With Advantage Bob counts his highest die twice; with Disadvantage he ignores his highest die. Advantage is not stackable. Advantage allows modification of an already-rolled result, and modification of some but not all uses of a roll. It is also a handy modifier for ad-hoc rulings.


 * Initiative Advantage doubles the high die only for the purpose of determining who goes first.
 * Hit Advantage doubles the high die only for the purpose of determining who wins the contest.
 * Damage Advantage doubles the high die only for the purpose of determining how many Victories the winner achieves. Damage Disadvantage can never reduce a successful hit to less than 1 Victory.

Take-Away Dice
Some actions can act on several targets, or in several areas, or over several rounds. Bob rolls normally for the first target, round, or area. Subsequent targets/rounds/areas use the same roll with the highest die removed after each area or round. Effect ends when highest remaining die < 9.

Area Effects: Take-away dice allow area effects to diminish away from the center of the effect. This allows area effects to be large without being either over-powered in total or under-powered at the center of the effect. Take-away area effects normally use a circular 15’ diameter center "ring" surrounded by 5’ wide donut-shaped rings. Each "May" takes damage at end of turn based on highest damage area which she occupied or moved through.


 * Instant TA area: 1 round, full strength at center, -1 die for each ring.
 * Expanding TA area: Multiple rounds, -1 die each round, first round affects center only, add 1 ring each round.
 * Declining TA area: Multiple rounds, -1 die each round, 1 ring is affected for every die > 8, full (current) strength on all affected areas.
 * Contracting TA area (Trap): Multiple rounds, double -1: -1 die each round and -1 die each ring, 1 ring is affected for every die > 8, full (current) strength only on outermost ring, -1 die for each ring (lowest at center).

Multiple Targets: Take-Away damage can be inflicted on several targets, at full effect for the 1st and -1 die for each subsequent target. For some uses multiple target will end on the first successful save, instead of when highest remaining die < 9.

Slow Rolls
When a random duration needs to be rolled, each roll should be delayed until needed. For example, if some effect is to last for 3d6 rounds then you roll 1d6. Roll the second die when the round count reaches the first dies result. Roll the third die when the round count reaches the sum of the first 2 dice. This simulates the character's uncertainty about the length of the effect.

Magic Numbers
Use Magic Numbers to simulate unpredictability. The Magic Number is a second random value derived from the same die roll by grouping the dice by the face (eg. 8) that they are showing and determining whether the count of dice in each group is even or odd. If the 10s group is even, the Magic Number is the count of consecutive even groups beginning with 10. If the 10s group is odd, the Magic Number is the negative of the count of consecutive odd groups beginning with 10. (Eg. a roll of 10 10 9 9 9 9 7 7 7 6 ... results in a Magic Number of +3 because 10s, 9s and 8s are even, but 7s are not.)

Much of the time a Magic Number only matters if it is less than -3 or greater than +3, but the Magic Number is always available for use if you need a quick random value. You can always generate a d4 value, and if there are enough groups you can generate a d8 value by looking at the two groups of dice which come after the Magic Number: if they match add 4 to the d4 result, otherwise use the d4 result as is.