Leicester's Ramble: Yet Another Mass Combat Hack - Using "Field Combat Rules for Shadowdark" in OSE

Sunday, October 19, 2025

Yet Another Mass Combat Hack - Using "Field Combat Rules for Shadowdark" in OSE

OK, for those who have been tuning in to the channel, we had a knock down drag out battle a couple of weeks ago in the campaign world.

There was strategizing. And cookies.

But prior to that, I needed to come up with a mass combat system for the session, something light enough that it didn't bog down our usual chaos. Plus I'd never run mass combat before. A couple of our crew have wargame and other miniatures battle experience, so I didn't want to look like a total noob.

So what to do?

Well, of course obsessively look for the "perfect" system through all the mass combat rules I've acquired. And then homebrew off the favorite. As you do.

So, this exercise wasn't completely cut from whole cloth. After looking at how I had already inventoried my spreadsheets of potential forces of allies and foes, I needed to find something that worked off a similar structure as to what I already had in mind and had modeled a bit in my prep.

So of the sheaf of options, I chose "Field Combat Rules for Shadowdark" by Connor Ludovissy for my starting point. The system starts with the extrapolation of an individual NPC combatant to a "unit" of similar capability. While Connor's assumption is five combatants per unit, my combatant number ("company") was more nebulous, in that it could represent a larger group of militia archers or a small group of elite knights.

For example, here is a unit of what may be considered militia from the original rules:

"2. Fighter Unit
Men and women with basic training and sharp weapons.
HP 24, AC 12, ATK 1, 1d8 damage, close
When half of unit is lost, DC 12 WIS or flees."

Very simple stats, and easily ported over to our B/X-OSE environment. In fact, I just kept the SD morale roles to simplify the number of dice on the table.

But the simple combat rules really stood out, especially since they give the option to give bonuses to units when PCs incorporate themselves into the unit, both for damage and morale. Field Combat Rules 4 and 5 line out most of this:

"4. Player characters may fight as individuals using their unmodified statblocks. However, characters with allies of a similar type may also form units, and their stats can be abstracted (adding additional damage and HP as indicated).
5. Any unit that is forced to flee leaves the battlefield and does not enter combat again. A friendly unit accompanied closely by a player character has advantage on WIS checks against fleeing from battle."

I modded it slightly: "Party members can either attack an individual target or add their damage to a unit & +2 morale." I figured that the miscreants would want to go stab the various big-bads directly, or step back and fire spells. Which they did.

Here's a couple of final example stat blocks, with a couple of different "Companies":

Opposing forces (mutant foot, cavalry, and chimera) had similar stats. Certain groups, like the undead soldiers and zealots, were exempt from morale effects.

As noted, I kept a similar number of hit points per company as Connor had in his units. Damage was based on an assumed HD average for the group: 1HD: d6, 2HD: d8, 3+HD: d10. Damage was also modified to reflect "averaging" effects of various attack abilities and bonuses, so we weren't getting bogged down if a mutant had an extra claw attack, or some chimera had poison or not. I can see adding a single extra "ability" for a group of combatants without too much complexity, such as a secondary damage or effect on a foe. I wouldn't go further than that in the spirit of keeping the combat light and fast. Connor recommends changing damage as the unit takes losses, so I would probably add a rule about dropping the damage die by one once the unit take half damage to represent their decreased effectiveness.

For our battle, groups of allied combatants were split out and printed onto individual sheets, so each player had their own batch of mercs and mooks to manage, between two and five groups. Likewise, they were in charge of moving the company's meeple, calling actions, and noting if the PC was in the group or separate. Late-arriving or reserve combatant units (such as the Khanate cavalry or the mutant chimera) were added to the field based on timer rolls.

I ran the opposing forces, both individual high-level NPCs/monsters, as well as the various combat units. For this battle, this involved rolling/selecting actions for about a dozen combat units and four NPCs/monsters. Although two NPCs got taken out in the first couple of rounds, simplifying my tasks...

Initiative was by side, the usual Dueling D6 of Doom per B/X-OSE (Connor also reverts to side-based initiative in his rules).

Overall, as an experimental method, I think it works well. I would need to refine it in the future, particularly with respect to PC values added to combatant units. I wasn't sure how to manage some bonuses, so we mostly just stuck with normal PC combat bonuses, although I may choose to stick to unmodified PC damage in the future (e.g. 1d8 vs 1d8+2 STR +1 magic). Something to refine. Otherwise, we didn't bog down or have too much ambiguity on what was happening, and the battle was regarded as fun. Which is what counts.

Connor's rules are seven pages in length (including cover). There is space left on a few pages for notetaking or homebrewing rules. The rules include unit examples, an example combat, and rules for training forces. I would highly recommend it for mass combat scenarios, as it can be readily modified for a rules-light combat, whether the opposing forces are a handful of skirmishers, or of multiple unit types and capabilities. Since the individual combat units are essentially NPCs, I wouldn't have any hesitation in dropping this into a one-shot or for people not familiar with mass combat. I would still use a battle map of some sort, as physically moving units and being able to visualize positions is helpful for immersion.

Other rules considered/read during the process: