GRENDEL MENDEL: Using Punnett Squares For Monster Design

Swine Chopper
from Darkest Dungeons

Once again I am surprised by what catches fire on Twitter and what doesn't. The most recent example is a response I posted to Luke Gearing and Sean McCoy's tweets about simple monster design. I agree with both in that it shouldn't be too complicated, but you do need some variation. To achieve that, I use a sort of "Punnett's square" based on [melee or range] x [dmg or special]. 

I created this method when trying to figure our how to further differentiate all the various factions in Forbidden Caverns of Archia. This megadungeon module has several factions that players interact with and I wanted to given them both a distinctive feel and strategic/tactical pros and cons. That way PCs could make informed decisions, based on their own party compositions, of who to interact with and tactics to use.

Here the basic Punnett's Square outline and below I will explain (1) how I envision each quadrant, (2) how this tool can be scaled to a small force, a singular "boss" monster, or a whole dungeon level, and (3) provide some examples.

The very basic square &
you most likely get it already.

I. Characteristics Of Each Quadrant

  • melee x damage: Enemies are characterized by how much damage they inflict and the melee weapons they use to do it: sword, axe, mace, or claws. The rank and file of an army or faction. The very basic unit.

    Generally I keep the damage to whatever weapon you use to define the melee "class". If in your game weapons have different qualities, such as in Luke Gearing's Wolves Upon the Coast, all the better. This might also be a could place to add an additional attack.

  • melee x special: For the exercise, I try to keep the damage at a 1d6 level but try to think of either (1) some unique way to deliver damage; (2) some unique effect on a successful melee hit in addition to the damage (which is why its kept low); (3) some spell-like effect that changes things while in melee. This quadrant might also include "attack animals" the (melee x damage) units might use.

    Now, since you are often running monsters in aggregate, I'd stick to just *one* additional effect and at the most two. This is because too many effects takes up DM brain-space.

    • Too quick!: Creature always attacks before PC
    • Charge: Creature moves in a straight-line anyone in between Save vs. Paralysis or take 1d6
    • Heavy hands: On a successful hit, save vs. paralysis or PC is knocked prone
    • Duelist: On a dmg roll of 1, save vs. paralysis or PC has weapon knocked from hand (may choose shield)
    • Grisly visage: Creaure has a 5' aura of fear
    • Mirrored image: Hard to focus on the true creature, first X attacks automatically miss
    • Trog stench: Foul stench makes it hard to hit
    • Spiky: Take 1 damage per round engaged in melee with the creature (pretty classic)
    • Web: Creature entangle on a successful melee (also pretty classic)
  • range x damage: Another basic rank-and-file unit armed with missile weapons. I also include reach weapons in this quadrant like the ever-useful spear. Other mundane sources of missile fire could be the old oil+torch or flaming arrows. Or it could be (melee X damage) units that first engage with 1 or 2 javelins before pulling out swords.

    For a touch more flavor, I might also just put very basic magic-users here with magic-missile-like attacks or ranged elemental damage. Could also be interesting reach weapons like a giant scorpion tail whip.

    For the armor of these units, I drop it 1 or 2 points below the (melee X damage) units and also give them a 1d4 melee weapon of last resort. However, if you wanted to express that what players are facing is a well-run military machine, these (range x damage) might just convert into (melee x damage) once the distance is closed.

  • range x special: When filling out this quadrant, I often don't even think about damage at all (but I don't exclude it). I am often trying to come up with fun, interesting, and thematic area effects (mundane or magical). And creatures with more spell-like effects that give boons and/or banes to friend and foe alike.


    • Fetid air: A creature carries a censer that casts fog or darkness
    • Standard bearer: A unit carries a banner that carries a magical effect or boosts morale
    • Dance of the dead: A creature can raise any dead on the battlefield or beats a drum that causes the dead to rise on a 5:6 every round
    • Anti-magic eye: a creature has a Beholder central eye on a stick directed toward magic-users
    • Spider climb archers: creature can climb walls/ceiling and fire from there
    • Shadow hands: The unit produces large, but clumsy hands from the corner shadows to grab
II. Scaling for different situations

At the basic level, I created this tool to create small skirmish-sized bands to take on 4-6 PCs plus some hirelings- here is a square I completed for the kobold faction in Archaia. Mainly, I thought they might employ insects in the area and tried to do some effects around poison. The black shapes are just a little reminder about the relative ratio of the units to each other using d6's and d4's.

The punnett's square for kobold

But the above could also be put together to represent a single monster with multiple attack types. While it might seem like a lot of actions its not when you look at even an average 1st level party of PCs in aggregate. A 1st level BX D&D party (fighter, cleric, wizard, thief) is a 4 HD creature (~11 HP) that gets about 3 attacks per round, maybe 2 spells, and on the opportunity to have 1 attack deal 2x 1d6 damage. Look at our kobold block above, we could turn it into some sorta scorpion-like avatar of a kobold god. 

So this single opponent is characterized by:
  • melee x damage: 1d10 (pretty standard) but maybe the front half is better armored AC +2 
  • melee x special: Since 2x1d10 damage is already strong how about "if hit, can crush for 1d6 damage per round, STR to escape claw"
  • range x damage: Stinging tail with 10' reach
  • range x special :
    • (v1): Again, since we already have 3 attacks, how about "can throw PC hit with claw 15' 1d6 damage if they hit another PC or solid object
    • (v2): Summon a swarm of insects to surround any target in line of sight; 1:4 drop weapon or disrupt spell casting
ADDITIONAL LINK: I think this method is a different way to look at Matt Colville's "Action-Oriented Monsters".

We also scale in the opposite direction and use the four quadrants to represent a whole level of a dungeon or maybe as a way to seed four ideas that can be iterated around to fill out a 6 or 8 entry encounter table.

Why might we use this method as opposed to just listing some monsters? The main benefit is that is it helps us remember to infuse some variety into our monsters. And this doesn't just have to be so "combat" oriented. Our "special" categories could before monsters that steal items, spoil rations, or weird magical effects that permeate the dungeon. The end result hopefully is a list of monsters that reinforce the aesthetics of the dungeon but are heterogeneous enough that a heterogeneous PC party (because you are rolling 3d6 down-the-line right?) can make use of a lot of its members in various encounters.

ADDITIONAL LINK: Again, the Punnett's square method here I think provides a more "back-of-the-envelope" alternative to Gus L's Dungeon of Sign very excellent post about creating unique monsters. Pairs well with what each monster might want or its objective in combat other than killing everyone. Something I've written about here.

III. Example with different sources: standard D&D monster & video game

First up is skeletons. Always a classic because with the hand-waving powers of "necromancy" you can do just about anything with them. Often they are just relentlessly attacking 2-3 HP creatures dealing 1d4-1d6 damage. This is especially triesome as a hoard, so I used to matrix here to bring some suprises like the drummer which can raise fallen skeletons as well as many dead hirelings. And I also tried to answer the question, "How would something like elven skeleons work versus the often assume human ones?"

I really like the video game Darkest Dungeon eventhough I think the actual dungeon exploration portion could be better done. It does have a nice tacticle combat though. The creature design of the swine is especially evokative and perfect for use in the square. Nothing too suprising here, just trying to mix basic melee and ranged units with some specials that provide themed support.

With the Swine more than the Skeletons, maybe having weapon differentiation is more important. So the Swine have hooks. Does this mean they can rip sheilds aways or try to disarm? Swine also have javelins which could be barrbed dealing more damage? Or maybe create a deep wound? Maybe it better fits when them to lower all damage dice 1 step (so base 1d4) to enhance the improvised, rusted, and wicked nature of the weapons through an effect.


  1. Complex monsters are delightful for their own sake, but yeah, not always the most workable at the table. I've done some work to bridge that gap; but your Punnett square idea is a good way to ensure some variety amid simpler monsters. I dig it.

    1. Thank you! Yeah, its certainly aimed at a sorta middle ground of "1d6 + 1 trick". But since you do these across 2-4 "units", there will be complexity with the interaction.