Rules v1.2.2

Dice System

As in many other tabletop miniature wargames, Jovian Wars uses dice to determine the success or failure of an attempted action on the table. Jovian Wars terms these attempts Tests or Rolls. For example, you might be asked to perform an "attack roll" or "skill test."


Jovian Wars uses a system of rolling a pool of six-sided dice to determine the Result of Test or Roll during gameplay. Generally, rolling a pool of X dice is represented as Xd6, i.e. rolling two dice would be represented by 2d6.

A successful Result in Jovian Wars involves having at least one set of matching die faces. For example, if you roll 2d6 and get the result 2, 2 that is a success as there are matching dice! A Result of 2,3 is considered a failure as no die faces match.


The more die faces that match, the higher the Magnitude of the Result. In other words, rolling three 3's is better than rolling two 3's. As a written shorthand for the Magnitude of a dice roll, we use the following notation where the result is enclosed in square brackets:

  • [N] - No Result - This represents rolling all unique die faces, i.e. no matches, and is considered a failure.
  • [D] - Double - Success, with two of the dice matching.
  • [T] - Triple - Success, with three of the dice matching.
  • [Q+] - Quadruple - Success, with four or more of the dice matching.

Adding a "+" to the notation is a way of denoting a minimum level or Magnitude of success. For example, a [T+] means that any result equal to or better than a Triple is successful. Quadruples are the highest level of success--getting five or more matching dice does not improve the level of success.


The actual die face rolled is often important also. If you roll two 2's, that is a double 2, and is denoted as [D2]. The Value of the Double result is 2.

You could also roll multiple matching sets! A result of [D2,D4] means you rolled two 2's, two 4's, and the rest of the dice have no matches.

Since an [N] Result has no matching faces, there is no Value associate with an [N].

Here are some examples:

Roll Die Faces Result Explanation
3d6 1,4,5 [N] Magnitude N, no Value
3d6 2,2,4 [D2] Magnitude D, Value 2
5d6 1,1,3,3,3 [D1,T3] Two Successes!

The last example has successes in its Result, one of Magnitude [D] and value 2, and one of Magnitude [T] and value 3. The Result could also be written as [D,T], [D1,T3], or even [D1,D3+].


In some cases, you will be asked to Esclate a successful Result, i.e. increase the Magnitude of the success.

  • The Value of the Result will remain the same.
  • You may not escalate a No Result [N] into a Double [D].
  • A [Q+] Result remains a [Q+] result.

Example: Dave fires a Nuke at a Capital Ship, and rolls a [D2]. The Nuke rules say to Escalate Attack Rolls, so Dave's [D2] result becomes a [T2] result.


In some cases, you will be asked to Diminish a successful Result, i.e. decrease the Magnitude of the success.

  • The Value of the Result will remain the same.
  • Unlike Escalation, you may Diminish a [D] to an [N].
  • The Value of the Result remains the same.
  • Regardless of how many faces match, a [Q+] Result diminishes to a [T] result, e.g. even if you rolled 6d6 and got six 2's, that [Q2+] becomes a [T2].

Example: Dave uses the Long Range Sensors Action to target a Capital Ship outside his sensor range. He rolls a [T4], but the Long Range Sensors Action requires you to Diminish your results, the final result is a [D4]. Had Dave rolled a [D4] initially, he would have Diminished it to a [N], and his shot would have missed.

Base Pool

The starting pool of dice used in a Test or Roll is usually defined by a model's attributes, its equipment, or its weapons. For example, a larger gun will generate a larger pool of dice during an attack.

This starting pool of dice is termed the Base Pool. The Base Pool can be modified to change the expected statistical outcome of the roll to model various in-game effects. For example, attacking the flank of an enemy ship is advantageous, so the Base Pool will improve. Conversely, an area of effect attack may be less effective against secondary targets and so the Base Pool will degrade.

Less than 2d6

In some cases, you might have a Base Pool of less than 2d6, either because the actual pool is less than 2d6 or it was modified to be less than 2d6, even negative!

In such a case, roll 2d6, regardless of the modified Base Pool size, but do not apply Flex Dice and the Macro Pool is considered to be 0, regardless of the effects of Armor, Attack Bonuses, etc.

Base Modifiers

Some effects may directly modify the Base Pool, either adding or subtracting dice to increase or decrease the odds of success, respectively.

Base Modifiers will be shown as follows

  • +Yd6 - Add Y dice to the Base Pool
  • -Yd6 - Remove Y dice from the Base Pool

Base Modifiers are the most impactful of the modifier types, as they increase not only the odds of rolling multiple of the same die face, but also the total possible number of matching dice in the set, i.e. you cannot roll a [T] with only a 2d6 Base Pool! Typically Base Modifiers represent large bonuses or penalties in combat, so they are the most impactful, increasing not only odds but also the magnitude of the success.

Example: A Base Pool of 3d6 is modified by +1d6. When rolling the Base Pool, you will roll a total of 4 dice.

Flex Dice

Sometimes you will be asked to roll Flex Dice, which are denoted +/-Yd6. If your Base Pool is Xd6, you will roll a total of X+Y dice. Once the dice have been rolled, you must remove Y dice from the rolled dice before calculating the result.

Flex Dice are less impactful than Base Modifiers, as the total number of dice in the result is the same. Your odds of rolling matching die faces is higher, but you cannot exceed a maximum result with X matching dice in the set. Flex Dice represent marginal advantages in combat, increasing the odds of a successful Result but not the magnitude of the Result.

Example: Dave's Pathfinder Squadron is attacking a capital ship target in the flank with Beam Projectors. The Anti-Capital rating of the Pathfinder's Beam Projectors is 2, which means Dave's Base Pool is 2d6. However, since the Pathfinder's are attacking the capital ship's vulnerable flank, they are granted +/-1d6 Flex Dice. To resolve this Attack Roll, Dave rolls 3d6, getting 4, 4, 6.

Dave must now remove a die from the rolled dice, so he chooses the 6, leaving him with a [D4] result! He could have removed a 4, but that would have resulted in a [N], which is decidedly worse than a [D4] result. Good job, Dave!

Macro Pool

Jovian Wars is a game of spaceships firing giant weapons at one another. To represent the magnitude of these guns, we make use of the Macro mechanic. The impact and force of these massive cannons or missiles just hit harder, they don't necessarily more often.

We model the increased impact with a separate pool of dice, termed the Macro Pool. The number of dice in the Macro Pool is typically defined by the "Macro" trait of a weapon, so a weapon with Macro: 2 would generate a Macro Pool of 2d6. You may want to have two different colors of d6's to allow you to simultaneously roll the Base Pool and Macro Pool simultaneously, removing the Flex Dice from the Base Pool as normal.

The Macro Pool may not generate a success in a result, but may increase the degree of the result. For example, let's say the Base Pool was 3d6, and the Macro Pool was 2d6. The Base Pool rolled 4, 4, 6, resulting in a [D4]. The Macro Pool rolled 4, 6. Since the double 4's of the base pool was a success, i.e. a matching set, you may increase the [D4] to a [T4] with the Macro die that rolled a 4. However, even though you rolled two 6's overall, the 6 rolled in the Base Pool was not a success, so you may not increase its degree.

Multiple degree improvements are possible. For example, if the Base Pool rolled a 4, 4, 6, and the Macro Pool rolled 4, 4, this would take the overall roll to a [Q4]!

There are effects that negatively affect the Macro Pool, such as various types of armor. In this case, you subtract the armor rating from the macro pool. This results in 3 possible outcomes:

  • Positive Macro Pool - Follow the steps outlined above.
  • Zero Macro Pool - Roll the Base Pool alone.
  • Negative Macro Pool - Roll the Base Pool, then downgrade Base Pool successes based on the Macro Pool roll.

For example, let's assume we have a Base Pool of 3d6 and a Negative Macro Pool of -2d6. The Base Pool rolls 4, 4, 6 and the Macro Pool rolls 4, 6. In this case, the [D4] result would be downgraded to an [N]! This is unfortunately slightly non-symmetric to the Positive Macro mechanic, but does provide another option in the design space to apply a penalty to a roll besides just removing die from the base pool.


A Re-Roll in Jovian Wars consists of performing a roll from the beginning of the procedure in its entirety. This means calculating the Base Pool, Flex Dice, and Macro Pool again, and re-rolling all of the dice together.

In practice, this is as simple as picking up all the dice again and re-rolling them, being sure to add back any Flex Dice that were removed.

You may only re-roll once, even if multiple effects would generate multiple re-rolls.