For Small, I'd have more than 4 in 2x2 squares; small creatures can fit in less than a 5' square. Say 6.To make a mob of (4) Goblins, take the standard Goblin statblock and apply the following:
-Increase it's area size by +1. Both small and medium creatures take up 1 square, so both are bumped to Large.
-Keep any traits/skills/senses that make sense. In this case, Nimble Escape allows Disengage as a bonus action. Hide as a bonus action may work in some cases, but DM can call that as it comes up.
-Add Swarm trait: a [size] swarm of Small humanoids. Can occupy another's space, can't regain HP or gain THP.
give it resistance to bludgeoning, piercing, and slashing damage. Usually I give advantage vs spells like Hold Person or Charm Person, but do what makes sense for you
-Multiply the HP by 2 (this takes into account the resistance)
-Double the damage dice to half the number of creatures in the swarm.
--For melee attacks they have advantage against any creature who is occupying the same space.
--For ranged attacks, the target instead makes a Dex save or take dmg, or half on a success.
Second, have in vulnerability to area effect damage instead of resistance to slash/pierce/bludgeon. So a fire bolt isn't 2x damage over an arrow.
A Large swarm of Small X would be 6 goblins.
Give it 5x HP. Give it 2x damage and 2 attacks, plus creatures who move adjacent or start their turn have to make a save or take 1x damage.
Large Swarm of Small (2x2 squares, 6 creatures): 5x HP, 2x damage, 2 attacks, 1x aura, 3x range
Huge Swarm of Small (3x3 squares, 12 creatures): 10x HP, 4x damage, 2 attacks, 2x aura, 6x range
Gargantuan Swarm of Small (5x5 squares, 32 creatures): 30x HP, 5x damage, 4 attacks, 5x aura, 10x range (5x5 area)
DCs and attack accuracy would also go up as the CR does.
Mob of Goblins
Large (Huge/Gargantuan 5x5) swarm of Small humanoids (goblinoid)
AC: 13 (15 w/ shields)
HP: 35 (70/210)
Vulnerability: spells that deal damage over more than 1 square of the Mob
Swarm: can occupy other creatures spaces, cannot regain HP or gain THP, can take 2 reactions (3,4) (no more than 1 per turn)
Nimble Escape: can take Disengage or Hide as a bonus action
Pack tactics: has advantage on melee attacks against any creature occupying its space.
Knives everywhere: if you start your turn within 5' of the Mob, or move within 5' for the first time on a turn, you must make a DC 12 dex save or take 1d6+2 (5) (2d6+2 (9)/5d6+2 (19)) piercing damage. If the Mob has attacked you since the end of your last turn you have disadvantage on your save.
Actions:
Mob: Make two Shortsword Attacks (two/four)
Shortswords: +4 to hit; 2d6+2 (9) P (4d6+2 (16)/5d6+2 (19))
Shortbows: target must make a DC 12 Dex save or take 3d6 (10) piercing (6d6 (21)/10d6 (35) 5x5 area), or half on a success.
Now lets try to balance them against just raw goblins.
Defensive CR: 1/8, 1/4, 5
Offensive CR: 4, 6, 15
Overall CR: 2, 3, 10
XP: 450, 700, 5900
Adjusted XP of "raw" Goblins: 300, 1000, 4000
CR if we hit Adjusted XP: 1.5, 4, 8
N^(3/2) Adjusted XP: 367, 1039, 4525
Target offensive CR: 4, 8, 11
DPR to hit target XP: (good) / 65 / 95
Revised:
Knives everywhere: if you start your turn within 5' of the Mob, or move within 5' for the first time on a turn, you must make a DC 12 dex save or take 1d6+2 (5) (2d6+2 (9)/5d6+2 (19)) piercing damage. If the Mob has attacked you since the end of your last turn you have disadvantage on your save.
Actions:
Mob: Make two Shortsword Attacks (three/three)
Shortswords: +4 to hit; 2d6+2 (9) P (4d6+2 (16)/5d6+2 (19))
Shortbows: target must make a DC 12 Dex save or take 3d6 (10) piercing (6d6 (21)/10d6 (35) 5x5 area), or half on a success.
New CR: 2, 4, 8
and these "Mobbed" goblins are worth "as much" as just using individual goblins.
I might be tempted to add in a "break up" rule as well.
Morale Failure: If the Mob starts with 10 / 20 / 60 HP or less, it breaks into individual goblins. For every 5 HP or fraction an individual Goblin (CR 1/8) is created in the space. 1d2 / 1d4 / 1d12 of them attempt to flee each turn, the remainder fighting back.
Or even
Downsized: If the Mob is reduced below 5/35/70 HP, it transforms into a single goblin/a large mob of goblins/a huge mob of goblins. When it does so it has to make a will saving throw against a DC equal to 10+1/2 of the damage that reduced its size or become frightened.
Last edited: