Open Mass Combat System (OMCS)

The Quintessential Fighter

The Quintessential Fighter

Author Matthew Sprange
Publisher Mongoose Publishing
Publish date 2001
OGL Section 15 qftr

The material below is open game content.

The Open Mass Combat System

The high level fighter is a leader of men, standing at the head of massive armies to fight for just causes and the defence of entire nations. Fighters of lesser standing may command an entire unit of fighting men within larger battles, battling alongside their comrades in the hope of eventual victory.

Whilst the main combat rules of the d20 system are superlatively detailed for most games, they tend to break down and become overly complicated when more than a dozen or so characters are fighting on each side in a battle. To handle much larger combats, a new system is required. The Open Mass Combat System (OMCS) presented here will allow combats to be fought involving hundreds or even thousands of characters on each side, greatly widening the scope of any campaign, The OMCS has much in common with the existing d20 system combat rules and players will soon find they can switch between the two quickly and easily, as and when their games dictate.

The intention of the OMCS, however, is not to super-detail huge sprawling armies and their use on the battlefield – there are hundreds of miniatures wargames available already that do this. Instead, the OMCS presents a realistic method of handling mass combats quickly and easily with just a few dice rolls, in order to allow the Games Master to concentrate on the actions of the true heroes, the player characters.

The OMCS was first presented in a cut-own form within our nautical supplement, Seas of Blood, where crews of fighting ships could engage in boarding actions to destroy their enemies. The full set of OMCS rules detailed here greatly expands upon these core rules, allowing multiple units of hundreds or even thousands of warriors to engage in huge, sweeping battles that may settle the destiny of kingdoms. Players will also be able to utilise many extra rules covering skirmishers, cavalry, siege engines and much, much more.

The Unit Roster

The Unit Roster Sheet on p109 is used to record the details and abilities of every fighting unit within an army. This sheet allows players and Games Masters alike to judge the effectiveness of any unit at a glance, and greatly aids combat resolution during mass combat.

The Unit Roster is used as a matter of convenience throughout these rules, from launching a devastating charge at an enemy to recording casualties when being pounded by fiery catapults. There are many circumstances in a game where the Games Master will prefer to use standard rules from Core Rulebook I to resolve combat and skill checks – the Unit Roster is used when large numbers of unit members need to perform one task at the same time.

A typical Unit Roster Sheet, detailing the newly recruited Fighting Men of Urusk, is shown below;

Race: Human Class: Warrior Level: 1
Unit Size: 80
Unit Type: Infantry
Unit Hit Points: 88 (+10% Constitution 12)
Initiative: +4 (+4 Improved Initiative)
Attacks: Short sword +2
Damage: Short sword 1d6+1
AC: 12 (leather armour)
Ability Scores: Str 13, Dex 10, Con 12, Int 9, Wis 11, Cha 8
Saves: Fort: +3; Ref: +0; Will: +0
Feats: Improved Initiative, Weapon Focus (short sword).

As can be readily seen, the Unit Roster has much in common with the monster entries of Core Rulebook III, as do the unit combat rules detailed below.

Race, Class & Level

Unit races and class are determined by simply majority – if a unit has 3 ogre warriors and 27 human fighters, the the unit will be noted as being human warriors. The level of any unit is considered to be formed by the average level or Hit Die of every member of that unit, rounded down.

Unit Size

This is simply a record of how many members are in a unit.

Unit Type

This is a refelection o fhow a unit operates upon the battlefield and will list either archers, infantry, skirmish or cavalry. The full rules behind unit type are detailed on p103.

Unit Hit Points

Unit Hit Points are used to measure the damage a unit may sustain in combat before being defeated or even wiped out. This is determined simply by combining the Hit Dice of every unit member, modified as follows:

Majority of unit has Constitution modifier +/-10% per Con modifier
Marority of unit has 3 hp or less -25%
Majority of unit has Toughness feat +10%
Cavalry unit +50%


This is the Initiative modifier (calculated in the d20 system way, using Dexterity modifiers, etc…) of the majority of the unit.

Attacks, Damage & Armour Class

These are determined by simple majority – the weapons and armour the majority of the unit are armed with are assumed to be carried by all for the purposes of the Unit Roster and unit combat. The majority of the unit are also used to determine base attack bonus and any modifiers for Strength for attack and damage, and modifiers for Dexterity with respect to Armour Class.


Any unit that has a majority of members with one or more identical feats will have such feats listed on their Unit Roster. However, the following feats have no effect upon mass combat and so are never listed, no matter how many unit members possess them. However, they may still use such feats individually when not using the OMCS rules.

Cleave, Combat Caster Defence, Combat Reflexes, Combat Rotation, Defensive Fighter, Deflect Arrows, Distract, Donning Armour, Expert Grappler, Expert Marksman, Fearsome Display, Great Cleave, Improved Armour Use, Improved Bull Rush, Improved Called Shot, Improved Disarm, Improved Dodge, Improved Trip, Mobility, Rest in Armour, Side by Side, Spring Attack, Sunder, Sure Aim, Team Flanking, Whirlwind Attack.

Ability Score & Saves

Once again, the ability scores and savers of the majority of the unit are noted down on the Unit Roster.

All entries on this wiki are published under the Open Game Licence Version 1.0a. See individual entries for copy of the license and declaration of Open Game Content.