Mob Combat

Mass combat can be simulated with a new set of rules, but converting the current set of rules is more economical and allows PCs to continue to act individually on a battlefield should they be of high enough level/power.

Any creature - humanoid or not - can be converted into a swarm for use as a mass combat unit. The default unit is ten individuals banded together, though one could just as easily do fifty or a hundred or a thousand (though at a certain point just, you know, narrate).

The basics are these:

- Start with the base creature's stat block.
- Increase the creature's size by two steps, listed as, e.g., "Huge swarm of Medium humanoids, unaligned"
- Multiply the creature's hit point total by the number of members of the unit (e.g., x10).
- Increase the creature's CR by +2.
- Give the creature the Unit feature: "The unit can occupy another creature's space and vice versa, and the unit can move through an opening as narrow as 5 feet wide. The unit can't regain hit points or gain temporary hit points."
- Give the creature the Mass Resistance feature: "The unit has immunity to the following conditions from effects that cannot target or affect at least 10 creatures or 10 squares of space: charmed, frightened, grappled, paralyzed, petrified, prone, restrained, stunned."
- Replace a creature's primary attack with a matching one using this format: "Concerted Thrust. Melee Weapon Attack: +5 to hit, reach 0 ft., one target in the unit's space. Hit: 21 (6d6) piercing damage, or 10 (3d6) piercing damage if the unit has half its hit points or fewer."
- Add multiattack if appropriate, allowing the unit to make its normal attack multiple times. Consider dividing damage (e.g., if it has multiattack that allows it to make three attacks, cut its attack damage to a third). Note that too many attacks obviate the entire advantage of the unit moving, striking, and taking damage as a single creature.

With these changes units can move and attack a single creatures, taking up blocks of space on the battlefield. The same rules allow for the creation of larger units, which simply increase the unit's size, hit points, and attack damage - all else is calculated normally. If the CR would push the creature up a tier of proficiency bonus then saves and attacks are recalculated as well.

Example creatures include:

Commoner Militia

Huge swarm of Medium humanoids, unaligned

Armor Class 10

Hit Points 45 (10d8)

Speed 30 ft.

STR 10 (+0) DEX 10 (+0) CON 10 (+0)

INT 10 (+0) WIS 10 (+0) CHA 10 (+0)

Senses Passive Perception 10

Languages Any one language (usually Common)

Challenge 2 (450 XP)

Proficiency Bonus +2

Mass Resistance. The unit has immunity to the following conditions from effects that cannot target or affect at least 10 creatures or 10 squares of space: charmed, frightened, grappled, paralyzed, petrified, prone, restrained, stunned.

Unit. The unit can occupy another creature's space and vice versa, and the unit can move through an opening as narrow as 5 feet wide. The unit can't regain hit points or gain temporary hit points.

Actions

Frenzied Beatings. Melee Weapon Attack: +2 to hit, reach 0 ft., one target in the unit's space. Hit: 10 (4d4) bludgeoning damage, or 5 (2d4) bludgeoning damage if the unit has half its hit points or fewer.

Archery Line

Huge swarm of Medium humanoids, unaligned

Armor Class 16 (studded leather)

Hit Points 120 (16d8 + 48)

Speed 30 ft.

STR 11 (+0) DEX 18 (+4) CON 16 (+3)

INT 11 (+0) WIS 13 (+1) CHA 10 (+0)

Skills Acrobatics +7, Perception +6 Senses Passive Perception 16

Languages any one language (usually Common) Challenge 6 (2,300 XP) Proficiency Bonus +3

Mass Resistance. The unit has immunity to the following conditions from effects that cannot target or affect at least 10 creatures or 10 squares of space: charmed, frightened, grappled, paralyzed, petrified, prone, restrained, stunned.

Unit. The unit can occupy another creature's space and vice versa, and the unit can move through an opening as narrow as 5 feet wide. The unit can't regain hit points or gain temporary hit points.

Actions

Shortsword. Melee Weapon Attack: +7 to hit, reach 0 ft., one target in the unit's space. Hit: 21 (6d6) piercing damage, or 10 (3d6) piercing damage if the unit has half its hit points or fewer.

Longbow Volley. Ranged Weapon Attack: +7 to hit, range 150/600 ft., one target. Hit: 27 (6d8) piercing damage, or 13 (3d8) piercing damage of the unit has half its hit points or fewer.

Bonus Actions Archer’s Eye (3/Day). Immediately after making an attack roll or a damage roll with a ranged weapon, the archery line can roll a d10 and add the number rolled to the total of the attack, or roll 3d10 and add the result to the damage dealt.