Chiron's Doom by Nick Bate is a gothic sci/fantasy-horror role-playing game about a (nigh-certainly) doomed expedition to a strange, alien monument of deadly mystery! This post is a run-through of some mechanical simulations I ran of the game, looking at how certain rules changes affect the its outcomes and how you can use them to tweak the game with specific goals in mind.
This post is about version 1.0 of Chiron's Doom! At least one other version was released (one was recently kickstarted) between version 1 and now, so I have no idea if these rules are how the latest version of the game works. This thread is just a demonstration using a game file I have; I'm not trying to keep it up to date.
Chiron's Doom uses a standard deck of poker cards (without jokers), with each rank+suit combination having a prompt in the game's oracle. Although it uses any of the cards in the standard deck, it doesn't use all of them at once or even in a single game. You start by making an “Expedition Deck” of the following 9 cards:
Then you make three “Disaster Decks”, one for each suit of Hearts, Clubs, and Spades. Each Disaster Deck contains the King of that suit plus 3 other random cards from that suit. The Disaster Decks come into play later, and add complications for the expedition to face.
Certain kinds of cards have mechanical changes attached:
Note: about shuffling, any time I say “shuffle into” above I mean the new card(s) are added to the Expedition Deck and then the whole Expedition Deck is reshuffled.
You draw the top card from the deck, follow the matching instructions on the oracle, then draw the next card and follow its instructions, and so on. The only mechanically distinct instructions are for the effects listed above; other than that, all prompts provoke a change in the story, usually a problem for the expedition to deal with.
The game ends in one of three ways:
This game's pretty suitable for simulating due to a combo of 2 reasons:
On point 1: each turn you choose whether or not to continue exploring, but that's the only mechanical choice you have. I'm ignoring it in these simulations; the expeditions here go on until they succeed or die.
On point 2: it's not just unconnected dice rolls; there are mechanical twists (e.g. adding Disaster Decks) and parameters/handles (how many Explorers you have, how many cards are in the starting and Disaster Decks, etc.).
I wrote some code to simulate this system in MATLAB, because that's what I've got at the moment, and ran 50000 simulated games for each set of conditions.
The three main things I'm interested in from the default rules are:
Note: Since you have to draw the King of Diamonds to complete the expedition (because it's a Diamonds card) and since each King kills an Explorer, it's possible for all Explorers to die and finish the expedition on the same turn. I recorded this outcome separately from success alone and death alone.
Here's the results for each outcome from 50000 simulated games:
So on average, successful expeditions are slightly shorter than failed ones (12–13 turns vs 13–14 turns) and the overall ratio of success to death to both is about 15100 to 32550 to 2350.
In other words, your expedition's about twice as likely to die as to succeed, with a very small chance of doing both at the same time. That feels like a pretty good balance for a game that's meant to be kinda pessimistic about your chances while stopping success from being too unlikely.
These tests show what happens if you change the number of Diamonds cards in the starting Expedition Deck (including the King of Diamonds):
These results are pretty expected. Adding more Diamonds makes games longer and death more likely, with successful expeditions slowly getting longer relative to failed expeditions the more Diamonds you add. Below 4 Diamonds you're actually more likely to succeed than die, but the games get real short, which we probably don't want.
These tests show what happens if you always or never include the Two of Diamonds in the Expedition Deck:
And the next results show what happens when you always include the Two of Diamonds, and increase the number of Diamonds cards shuffled into the deck when you draw it:
Always including or excluding the Two of Diamonds has a small, but significant effect on outcomes and game length. Shuffling in more Diamonds has a few obvious effects, the same as adding more Diamonds to the starting Expedition Deck.
These results show how changing the size of the Disaster Decks affects the outcome (all Disaster Decks are given the same number of cards):
The handy thing here is that making the Disaster Decks bigger or smaller only affects game length, not outcomes. Intuitively, this makes sense (bigger Disaster Decks dilute the Expedition Deck's Diamonds, but also dilute the Kings).
These results show how adding another Explorer and/or making the King of Diamonds uniquely kill 2 Explorers affect the outcome:
Now these change a lot. Obviously, killing 2 Explorers when you draw the King of Diamonds makes total death even more likely. This not only shifts the success-to-death ratio from 1:2 to 1:10, it also evens out the chance of success alone vs the chance of succeeding and dying. Basically it's a way of instantly making the game much more brutal (and a bit shorter).
Changing to have 4 Explorers and only killing 1 on each King obviously has the opposite effect: longer games that're way more likely to end in success than death (inverting the 1:2 ratio into a 2:1 ratio). It also has the tiny effect of making it possible to draw every card in the deck in a single game, because having an extra Explorer means you can draw every King before they all die.
Making both changes is very similar to the default, but with a slightly lower chance of death and a proportionately much higher chance of dying and succeeding on the same turn. This adds an interesting wrinkle to the default scenario.
I could've recorded the number of Disaster Decks shuffled into the Expedition Deck over the course of each game and how that changes with each mechanical change, but I don't think it'd be super useful to look into that, because of a combo of these two factors:
So we can tell we're much more likely to get 2 or 3 Disaster Decks than 0 or 1 no matter what changes we make to the game. Maybe there's something a little interesting that could be uncovered here, but I don't wanna double the number of plots in this post just on that tiny off-chance of a slightly-notable result.
I did think about testing what happens if you remove one of the Disaster Deck triggers (the Two of Hearts, Clubs, or Spades) from the Expedition Deck, but that'd cut off a whole quarter of the oracle and a big chunk of prompts, so I didn't bother (also I think the outcome would be 1) very obvious and 2) very extreme).
My code's set up so any of the changes I made can be applied in any combination, but running every combo would bloat this post and my gut feeling is the game's not complex enough for those combos to have unexpected results. One change might blunt or amplify the effects of another, but I doubt there'd be any surprises. Maybe I'm wrong! But I'm not too bothered if I am.
Adding more Diamonds cards, no matter where you do it, always makes games longer and more likely to end in death.
Making Disaster Decks bigger or smaller doesn't make the expedition more likely to succeed or fail, it just affects the probable length of the game.
Adding an Explorer or making the King of Diamonds more lethal have very strong, obvious effects on game length and outcomes. Make both changes and they balance each other out, aside from making the simultaneous success and death outcome a bit more likely (particularly in games that run out the deck).
Adding an Explorer would obviously add more character setup and change the group dynamic, but would be suitably ominous in cultures where the number 4's linked to death. I dunno what the King of Diamonds prompt would be, to kill 2 Explorers instead of 1 (maybe the monument figuratively or literally “selects” people to live or die, revealing a secret about itself in the process?).