On Combat (Them Deeper Bones, design diary 3)

Petri Leinonen
5 min readMay 1, 2021


Them Deeper Bones is an OSR-adjacent retro adventure game I’ve been working on since December 2020. The current full text (version a.7.7 at the time of writing this design diary) can be found at https://themdeeperbones.com/. I started writing these design diaries quite late into the process, early ones like this will focus on things I’ve already done and let me ponder on why I’ve done them.

A huge part of the mechanical bits of the game focuses on combat, as outside of that things can mostly be solvable through role-playing. So this time I’ll focus on what makes the combat tick, and why. Especially the Damage system (damage and banked dice) and Initiative.

A chess player moving a white piece towards a slew of toppled over black pieces.
chess moves forward

Rolling the Hit Dice

The humble beginnings of Them Deeper Bones lie in two discussions I had before I started writing it. One was a repeating chat about combat in tabletop RPGs, and how many times the only real reason there are hit points in a system is to make combat last long enough for the characters get to use their super cool combat abilities and how that generates by the numbers encounters that grind on at a predictable pace. The other was an off-hand comment in a wider topic of someone I can’t credit, who pointed out that in generic D&D, “If you squint hard enough, a single successful generic attack removes a single hit die from an enemy.” And how that has a grain of truth to it, especially when looking at earlier systems where the numbers haven’t been pumped up to accommodate for the first discussions grind.

So, sometime in December, I made a small damage hack that is the first rule written down for Them Deeper Bones. When you hit someone, you roll your weapon’s Damage Dice, and they roll their Hit Dice. And if your roll causes enough damage compared to the Hit Dice roll, you take that particular Hit Die away from the target. Multiple if you’re really lucky and they’re unlucky. And if you don’t get a high enough roll, the battle continues without effect.

A simple change from whittling down a gauge to an either-or result, and suddenly, combat wasn’t a grind, but unpredictable.

Banking Dice

But unpredictably isn’t great or any better than the grind if not implemented properly. When I actually playtested the rule, the game showed me why. D&D’s base combat cycle already has a huge issue with wasted actions. When you declare an attack and miss, nothing happens. This is of course mitigated somewhat by there being a lot of other elements to combat than just the basic attack, but still, there is a good chance that a player of a hack-and-slash focused character will spend their time accomplishing nothing if the dice are against them. And now, with damage roll being something that either does something or doesn’t, it became a game where you could fail at two points of the roll to accomplish anything at all.

Enter banked dice. So, when you are hit (the attack roll succeeds) but not damaged (you don’t lose a Hit Die), the Damage Dice that were rolled in the damage are banked (stored on you), and rolled again with the Damage Dice the next time you are hit in addition to the damage dice the attack itself brings. So if earlier in the combat you were hit twice with a sword (1d6 damage) that didn’t manage to take down a Hit Dice, and now someone hits you with an improvised weapon (1d4 damage), the Damage Roll they make is 1d4 (the attack’s damage) + 2d6 (the two sword hits from a few seconds earlier). And if any of them gets a result that matches or is greater than a result on your Hit Dice, you got damaged and lose a Hit Die. While the sword hit wasn’t one that instantly took you down, it had an effect.

Once you lose a Hit Die, banked dice are removed and counting hits begins anew.

Oh, side note, the first level characters have one Hit Die. It’s tense and fun to roll your single Hit Die and see if the third successful attack on you is finally the one that takes you out or if you’re lucky again.


Once I had the basic damage cycle down, I did some fine-tuning here and there to the combat numbers — switch to ascending Armour Class, get rid of the 5 foot square, etc. And thought “well, might as well start fixing other issues I have with these sort of games.” And that’s how the combat hack turned into a game.

One thing I did for this project was start studying on the old material with a clear purpose. And ran across AD&D 2nd edition’s initiative system. Which flips the script from what we these days think of with initiative. In AD&D2e, you declare actions first, roll the order of actions second, resolve them after that. I ran a playtest with this, and loved it.

What the declare actions first does is break the modern cycle of A character executes an action—Situation gets updated — Initiative moves forward—Next player spends a moment to assess the new situation—They commit to an action—Their character executes that action—Situation gets updated—Initiative moves forward, that makes combat really slow. When everyone commits to actions first, they are all acting on one situation and one set of assumptions. And can do the assessment simultaneously. This speeds up things by a mile.

However since everyone makes their decisions blind, it can be a bit of a random game. So, I updated the initiative system a bit further—In TDB, the GM decides and declares the actions of their characters first, and the players can make their decisions based on that with the uncertainty being the order they are acting in. This is to keep the puzzle like nature of the game going. (Of course there is also the exception of creatures that have an Alien level of sentience that declare their actions after the players do, but that’s more to provide a different sort of challenge in rare occasions.)

Parting thoughts on combat

The common criticism of many RPGs is how too much of their rules focus on combat, and that games should really focus on something else instead. It’s so common that I‘ve voiced it myself many times on several occasions.

In the current version, the combat rules in Them Deeper Bones are 9 pages (out of a 100). In addition, for example the fighter role has a lot of abilities that do nothing outside that particular frame.

It’s a lot, for a game that is not about the combats. But it has that emphasis because a) I want the combat to provide a challenge, b) I don’t want to force people to role-play out the very tactical situation that is combat, and c) I want the combat to be a tense and interesting challenge as it has a prevalence in the fantasy RPG genre. I hope you try out how it works and let me know what you think.