Thrice RPG and Dice

Thrice is an RPG game that recently lauched on Kickstarter. I won’t post the whole Kickstarter detail, but I thought the custom dice are interesting.

A light engine TTRPG with a solid structure, using only d³s.

Thrice Fantasy is a flexible and comprehensive TTRPG, with a fresh and flowing gameplay. The rulebook allows you to play in fantasy settings. Thrice Fantasy is the first product to use the Thrice engine, a rule system that will be employed in various styles and genres, as we’ll explore in upcoming Thrice-based releases.

You can find more detail at the Thrice RPG kickstarter.

Thrice Dice

Thrice uses special six-sided dice on which the number 1 appears on one face, 2 on two, 3 on three. These dice are d³, pronounced “d-thrice”. One d-thrice is referred to as 1d³, two dice as 2d³, and so on.

Each die rolled in the game aims to obtain a target number, which can be 1, 2 or 3. If the result of a die is equal to the target number, that die scores a success. The target is indicated in round brackets after the number of dice. If a trap inflicts 5d³(3), the Master rolls 5 dice: each result of 3 represents one damage inflicted.

As an alternative to d³, you can use ordinary six-sided dice (d6). In that case, if the result of a die is equal to or less than the target number, that die scores a success.

This breaks down to:

need a 1: 16.6% (1 in 6 chance)
need a 2: 33.3% (1 in 3 chance)
need a 3: 50%   (1 in 2 chance)

Using a d6 as suggested would be:

need a 1: (roll a 1)      : 16.6%
need a 2: (roll a 1, 2)   : 33.3%
need a 3: (roll a 1, 2, 3): 50%

Rolls of 4-6 are ignored. I don’t really like the idea of ignoring dice like this, as the tend to clutter up the dice pools when rolling.

If you want to play around with anydice.com, this formula is for the example given 5d³(3)

output [count 3 in 5d{1, 2, 2, 3, 3, 3}]

Chances of each result (counting how many 3s you get):

0 "3s":  3.125%
1 "3s": 15.625%
2 "3s": 31.25%
3 "3s": 31.25%
4 "3s": 15.625%
5 "3s":  3.125%

The below is a distribution showing 8d³(3). As the rules haven’t been published yet it’s hard to tell how many dice are actually needed during a normal session.

Given that needing a result of (3) is just a 50% distribution this graph makes intuative sense.