So, I’ve been thinking a lot about the sun the moon recently. Not the heavenly bodies (well, I always think about those, but not more than usual!), but rather a die mechanic I’ve been noodling on that I’ve been calling “sun and moon dice” or “celestial dice” until I either think of a better name, or, more probably, decide this name is fine and give up on thinking of a new one.

Update (12/21/24): I ended up using this in AM&R. It was not a big hit.

Backstory

As anyone who hangs out with me on Mastodon probably knows, I’ve been working on the second edition of my first self-published game, Hespera, for a while. My largest self-published game, Ikaros, is (if I could toot my own horn for a second) a lot of fun, so I was really excited to rebuild Hespera 2e on top of the Ikaros engine! However, as anyone who hangs out with me on Mastodon also probably knows, this has been a bit of a struggle.

The elephant in the room is this: Hespera, from its outset, was a very rules light game. I’ve never described it as a micro-RPG, but it’s definitely a mini-RPG. I wrote it with a constraint of 12 digest-sized pages of rules, and 12 digest-sized pages of setting info (the setting info has since expanded past 12 pages, because I just love the dang setting so much!). Ikaros, by contrast, is about 40 A5 pages of rules, and that’s even before getting into stuff like talents, rituals, and various other lists-of-stuff chapters!

I had a big brainstorm session, and one of the rules that came out of it was a change to resolve combat in a single roll, rather than having a traditional to-hit roll followed by a damage roll. This won’t really save me a ton in terms of rules space, since skills and conditions take up the vast majority of the rules, but I’ve been reading a lot of blog posts about overloading dice.

While there’s tons of prior art here about overloading attack and damage dice (and even an entire system, One Roll Engine, named for the concept), this is the way that I can take that concept and easily port it into the “Xd6 keep 2” system I’ve been unable to tear my brain away from for the past four years.

Mechanics

These mechanics are so simple that I actually feel kinda weird making an entire blog post about them, but honestly this post is really just a vehicle for the big table of results at the bottom.

The big idea here is that after rolling, you’re trying to determine which die is your celestial die. Your moon die is the lower of the two dice, your sun die is the higher of the two dice, and your stars die is half the moon die, rounded up (in other words, reading the moon die as a d3 instead of a d6).

1. Roll your dice, choose which two to keep, and add any static bonuses (such as skills). Compare the result to the target number (usually between 8 and 14; in combat situations the target number is your opponent’s roll to dodge or shoot you back or whatever) and threshold (between 2 and 6; in combat situations the threshold is the opponent’s armor value).
   • If you roll less than the target number, your stars die is your celestial die.
   • If you roll equal to or higher than the target number, but less than the target number plus the threshold, your moon die is your celestial die.
   • If you roll equal to or higher than the target number plus the threshold, your sun die is your celestial die.
2. Then, deal damage equal to your celestial die, plus any static bonuses. Ta-da! That’s it.

Here’s a big ol’ table with all the expected results from needing to hit certain normalized TNs compared to various thresholds. For each combination of normalized TN and threshold, the table lists the total average of the celestial die, the average of the sun die, the average of the moon die, and the average of the stars die. The number in parentheses next to the average total average is the number of times a sun or moon was selected as the celestial die. For each of the celestial averages, the number in parentheses is the number of times that specific die was selected as the celestial die.

Results

The code to generate the table can be found here.

Other ideas

I originally thought this through to replace a separate damage roll in combat, but it opens up some neat possibilities!

Incentivizing choosing different dice

Since there are ways to get bonus dice rolled but not bonus dice kept, it could be used to incentivize choosing a pair of dice that aren’t just the two highest. These two are also super thematic for ritual rolls.

• The celestial die could impose a cost of some kind, in which case you’d want to make sure to roll high enough to succeed, but low enough to keep the moon die instead of the sun die.
• Alternatively, the cost could be proportional to the difference between the moon die and sun die, which would encourage trying to get as close to pairs as possible.

Playing around with the numbers

There could also be ways to allow for some kind of supercharging in the presence of certain talents or abilities.

• If you succeed well enough (or use a special rule?), maybe you could have an eclipse die, whose value is equal to your sun die plus your moon die, or a stellar die, whose value is equal to your sun die plus your stars die.

Closing

Anyway, let me know what you think! I’m probably gonna keep noodling on this further, but I think there’s potential! As always, you can reach me on Mastodon at jewelpit@dice.camp.

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