Dice Pool Rationale

This archive page preserves the reasoning behind the shift from the traditional d20 system to a d4 dice pool mechanic.

The d20 Test system (used in D&D 5e) is simple and widely recognized, but suffers from:

• High variance: Every number from 1 to 20 is equally likely.
• Poor skill reflection: A highly skilled character can still roll a 1 and fail, while a novice can roll a 20 and succeed.
• All-or-nothing feel: Pass/fail results flatten tactical depth.

The d4 pool system emerged from a desire to:

• Reduce swinginess through bell-curve probability
• Make character building choices feel consistently impactful
• Naturally scale with character growth

If we were to simply change from using a single D20 to using a number of D4s we could roll a number of D4s equal to:

• Attribute modifier
• Plus Proficiency bonus (if applicable)

You sum the results. For attacks or spells, include the weapon or spell’s damage die in the roll.

Then:

• Subtract target’s Evasion or DC
• The remainder is damage (or effect strength)

Example: A fighter with +3 STR and +2 Proficiency uses a longsword (d8). They roll 5d4 + 1d8, subtract the target’s Evasion, and apply any remaining value as damage.

Note that the max roll of 5d4 is 20, simulating a D20 roll but with a smooth bell curve.

By reducing your dice pool with each action, the system naturally limits multi-action abuse:

1. Start of round: Action Load = 0
2. Take action: Add 1 to Action Load
3. Dice pool for next action = Normal total dice − Action Load

This replaces D&D’s Action/Bonus/Reaction system with something more fluid but self-limiting.

Modeled as adding or removing d4s:

• Advantage: Add a d4, remove the lowest die rolled
• Disadvantage: Add a d4, remove the highest die rolled

Multiple stacks add/remove more dice. It’s a smooth mechanic that stacks intuitively.

For powerful effects (like spells with high damage), the player may:

• Sacrifice one of the damage dice
• Add it to the attack roll to boost success
• Omit it from damage if the spell hits

This creates tactical tension: ensure a hit, or go for full damage?

• If a player-initiated action would roll 0 or fewer dice, it can’t be attempted.
• If the GM calls for the roll, the player always rolls at least 1d4—even with negative modifiers.

• High-tier abilities can require a minimum pool (e.g., “Fireball needs 6 dice to cast”)
• Dice serve both as resolution and resource tracking
• Everything stays visible and tactile—no hidden math

• Probability modeling: https://anydice.com/program/3c172

At first glance, using a pool of D6s might seem better than a pool of D4s. The variance is greater while still being a solid bell curve of probability. But there are a few problems.

The first is that when rolling D6s it is harder to easily total the results. Using D4s leads to most rolls are mostly pairs adding to 5, making addition quick and easy. That isn't true with D6 pools.

The second is that the variance between low-skilled and high-skilled characters is too vast. Trying to determine the number of dice to roll matches up pretty well with D4s but not D6s. An example might clarify.

So this means we would either need to create a different method of figuring out how many dice to roll, or expand the way we calculate success/failure. Doing the latter adds the problem of converting from standard D&D sources.

But by staying with a D4 pool we can easily calculate the number of dice while making translations from D&D sources a breeze.