Basic Game Mechanics

Rulings, Not Rules
These are not rules, they are guidelines to help the GM make consistent rulings. These guidelines are a resource for the referee, not for the players. Players use observation and description as their tools and resources. Moreover, these guidelines are not intended to cover all possible eventualities. The GM will use his judgement to resolve any unexpected situations.

Role-Play, Not Roll-Play
Isekai is a game of skill in a few areas where many games just rely on die rolls. You don’t have a “spot” check to let you notice hidden traps and levers, you don’t have a “bluff” check to let you automatically fool a suspicious city guardsman, and you don’t have a “sense motive” check to tell you when someone’s lying to your character. You have to tell the GM where you’re looking for traps and what buttons you’re pushing. You have to tell the referee whatever tall tale you’re trying to get the city guardsman to believe. You have to decide for yourself if someone’s lying to your character or telling the truth.

No Limitations
In Isekai a player can describe and attempt virtually anything he can think of. He doesn’t need to have any sort of game-defined ability to do it. He can try to slide on the ground between opponents, swing from a chandelier and chop at a distant foe, taunt an opponent into running over a pit trap ... whatever he wants to try. That doesn’t, of course, mean that he’ll succeed. It’s the GM's job to handle these attempts colorfully and fairly, choosing whatever probability he thinks is the right one and rolling some dice.

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 your foe with no dice, you get 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).

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.

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.

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

Combat Rounds
Simultaneous Action-Rolls are compared to determine initiative. Then each Action-Roll is compared to the target’s Defense-Roll to determine success and Victories.

Conceptually all actions begin at the start of the round, and are complete when it is the characters turn to act. In many modern FRP systems an average round is 6 seconds. Isekai rounds are more flexible, but should not on average exceed 10 seconds.


 * 1) Check NPC Morale
 * 2) Each character states her intended action and target, and calculates how many d10 to roll. This action and target cannot be changed except as noted in Combat Options and Maneuvers.
 * 3) All PCs and NPCs make Action-Rolls simultaneously.
 * 4) All Stun Damage is removed from all characters. (This reduces the Damage Penalty to Defense Rolls.)
 * 5) The character with the highest Action-Roll result performs (or cancels) her intended action.
 * 6) The target of that action makes a Defense-Roll. If the target has not already acted in this round, taking damage causes his action to automatically fail (but see Suicidal Action).
 * 7) Both characters make any Second-Rolls (if any) to determine Victories.
 * 8) Repeat steps 5, 6 and 7 for each character in descending order of Action-Rolls.
 * 9) “Free Speech” phase: Insults, surrenders, attempts to negotiate, cries for help, etc.

Thresholds
In some cases your Action-Roll must exceed a certain Threshold for your action to succeed. If the Threshold is not met there is no need for a Defense-Roll. In most cases only the Thresholds divisible by (should I use 3 or 4?) are used.

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 used 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 you count your highest die twice; with Disadvantage you ignore your highest die. Advantage is not stackable.
 * 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.

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.

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.

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.

Roll until Ready
Deletion of this section has been proposed

Some actions can use a slower, but more careful method. The initial effort takes 1 or more minutes. Your initial roll must exceed any required Threshold. If you then don’t like your roll, you can re-roll 1 die by spending additional time in the attempt. Each re-roll takes twice the time of the previous roll. When you achieve a roll you like, defense is rolled to determine the result.

This is a response to players wanting to repeat failed skill attempts. Once defense has been rolled, no further attempts are possible.

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.)

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.