My wife recently gifted me the Candela Obscura Core Rules book as a birthday present. It has some interesting new mechanics, which are refreshing to a game master that has been playing only Dungeons and Dragons 5th Edition for the past 4 years. Candela Obscura is based on the Illuminated Worlds System and uses six-sided dice (d6 for short) instead of twenty-sided dice (d20) to determine the impact fate has on the characters’ actions. In this article, I want to explore the statistics behind this system and to see if spending resources will help the players get to a successful action. I will briefly summarize the relevant rules below, but if you want to read the official version I suggest you buy the book or read the free quickstart guide.
The Illuminated Worlds system uses a dice pool of up to six d6. You roll the entire pool that you are allotted for that action, and only look at the highest results. On a 1 – 3 result, the roll is a failure. You don’t get what you want, and suffer the consequences laid out by the game master (or Keeper as it is called in Candela Obscura). On a 4 – 5 result, the roll is a mixed success and you get what you want, but there are some consequences. On a 6 result, the roll is a complete or full success and you get what you wanted without major consequences. If you manage to roll multiple 6s, the roll is a critical success. You get what you want and more.
To determine the size of the pool of dice you get to roll, you have to check your character sheet. For each Action, you have a rating from 0 – 3. The rating indicates the size of the dice pool. You can increase the dice pool by spending “Drive” points. For each Drive that you spend, you can increase the dice pool by one die up to a maximum of 6 dice. You can spend as many drive points as you like, as long as you still have them available. If you have an ability rating of 0 and choose not to spend Drive to increase the dice pool you can still attempt the roll. In that case you roll 2d6 and take the lower result. If you do it this way, you cannot get a critical success. Other players can also spend their Drive points (maximum of 1 Drive per player per roll) to increase the size of your dice pool.
The main questions that now arise are what are the odds for success (mixed, full or critical), and is it worth spending Drive to increase the odds? To answer that question, we can calculate the probability of certain outcomes using the binomial distribution. The results are split out in Table 1 for the total probability of any form of success, just full or critical success and critical success.
| Number of dice | Mixed, full or crit. | Full or crit. | Crit. |
|---|---|---|---|
| 0 | 25.0 % | 2.8 % | Not possible |
| 1 | 50.0 % | 16.7 % | Not possible |
| 2 | 75.0 % | 30.6 % | 2.8 % |
| 3 | 87.5 % | 42.1 % | 7.4 % |
| 4 | 93.8 % | 51.8 % | 13.2 % |
| 5 | 96.9 % | 59.8 % | 19.6 % |
| 6 | 98.4 % | 66.5 % | 26.3 % |
I find it interesting that the probability of any form of success is actually quite high for most rolls. Even if you only have 2 dice in the pool, you are likely to get be successful in your endeavours. Most of the time though, your success will come at a cost (44.4% of the time you will have a mixed success). This will drive the story forward, but will probably give the players the feeling that they are not getting things for free. If your character specializes in certain abilities and manage to eventually increase their rating to 3, they are successful most of the time. I wonder if this is a deliberate design choice for the Illuminated Worlds system, or whether this was just the result of playing around with potential mechanics and the open beta phase.
Spending Drive points can certainly be worth it, but there are (strong) diminishing returns. Especially if your dice pool increases beyond 3 dice, spending that Drive becomes relatively expensive and is probably only worth it if you need that full success. But, like most things in gaming, it is up to the player and the in-game circumstances to determine what is the best course of action. Or more importantly when playing a fiction-first roleplaying game like Candela Obscura: what helps me tell the story that we want to tell? Even though it is a game, it is the collaborative storytelling that makes tabletop roleplaying games memorable. It is rarely that players will remember that they had that one critical success, but they will remember – and tell stories about it out of game – that they managed to beat the monster when it counted. Preferably in an epic way.
Anyway, I look forward to playing this soon with one of my gaming groups and will append this article with actual play experiences if necessary. Enjoy playing!