I came up with some streamlined mass combat rules to handle a battle in my Reavers campaign with 30+ participants on each side. It worked pretty well, so I thought I’d share it. I didn’t want a huge system, but I wanted something that would work smoothly, that would incorporate the PCs organically without turning into some weird “minigame” or requiring them to be commanders.
Quick Mass Combat Rules
Army Builder ™
Break each side up into units of n creatures, where n=5, 10, or whatever makes sense for the scale of the conflict. Units should be mostly homogeneous.
Unit Initiative = Median initiative of the creatures in the unit.
Unit HD = Total HD of the creatures in the unit.
Unit hp = Total hp of the creatures – break them up into n boxes of equal hp, one box per creature.
Unit AC = AC of each creature.
Unit Move = Slowest move of the individual creatures. Loosely track units on the battlefield so it’s clear who they’re in contact with.
Unit Attack = Normal attack bonus of the creatures + ½ times the number of creatures in the unit. (10 creatures = +5 attack bonus.)
Unit Damage= normal damage + the number of creatures in the unit. (10 creatures = +10 damage.)
Saves = save of each creature.
Targeted spells can only take out the appropriate number of individuals.
Area effect spells, apply as unit damage. Might not be “fair” to the fireballers, but whatever.
Named NPCs and PCs can engage specific targets in the unit, and get engaged by them separately from the unit attacks.
Units roll once to attack other units using their unit attack versus the other unit’s AC. If they hit, they roll damage, duh. As a unit takes damage, you cross off boxes for each creature-sized increment of damage they take. You can “half cross” off a box for leftover damage that’s about half a creature’s hit points. As armies take damage and boxes get crossed off, their attack and damage bonuses based on the number of creatures in the unit go down commensurately.
After that, it’s rulings not rules baby!
A pirate attack on a Chelish manor house! There are 30 attacking pirates, and they have a wagon-mounted swivel gun. Each pirate is a War2 with Toughness – they have 20 hp each, but only attack at +3, do 1d6+1 damage each and have an AC of 13. The PCs are their “men on the inside”.
The keep is defended by 30 human guards (War1) with only 5 hp, but AC 17 and damage of 1d8+1 (longsword +3). It is also defended by 10 orc soldiers (was 15 before the PCs got their hands on them) that are War1s but have an effective hp of 22 because of their orcish ferocity, AC 15, and attack with a greatsword at +5 for 2d6+4 points of damage.