This week was rather hectic, between scheduling issues at work and a nasty power outage. Therefore, I didn’t get to edit this article as thoroughly as I would have liked. If it comes off choppy, I apologize.

I’m going to present you with a monster. I want you to tell me what’s special about this monster? What makes it different?

Ready? Here it is.

Now, what’s special about it? Get it in your mind, write it down, say it out loud, whatever. If you’re in the future, then store the thoughts in your psychometric PAN cloud. Now tell me. What’s special about it? What’s different?

…

That’s right! Octopus Telepathy, Underwater Camouflage, and a poisonous bite. You get a cookie.

Now, can you tell me why?

…

You only knew that because of the title of this article. Cheater. I hope you choke on that cookie.

Darwinian monster evolution has never really been a topic of intrigue or discussion in D&D. Monster variants have been toyed with, of course, but no one ever really took the initiative and answered the question of “what WOULD a tropical sahuagin be like?”

Back at the tail end of 3e, when Monster Manual 4 came out, it contained some variants for certain previously-published monsters. Orcs, gnolls, and various other beasties got special stat blocks for scout, battle-priest, and slave-takers. This was, of course, doing the same job as the Tome of Battle: preparing us for 4e. However, even with these variants, they were only ever contained within the idea of roles within a monster community. The Pathfinder Monster Codex basically does the same thing for its system, establishing various priests, scouts, and soldiers using a basic monster as the template.

4e, of course, for anyone who read its monster manual, turned this idea up to 15. There are, like 3 different kinds of Aboleth in that book. ABOLETH! Really? The normal psychic monster-fish wasn’t doing it for you? You needed Lashers and Slime Mages to flesh out your epic, tactical all-aboleth skirmish? However, among all the Shadar-Kai Chainmasters and Magma Striders, 4e did flirt with the idea of monsters that evolved to suit their environment. Granted, it was 4th edition, so the monsters all came out looking like the kinds of re-skinned enemies you’d fight in an early, low-memory Final Fantasy game (THIS centaur is different, because its sprite is completely orange and it uses FIRE BREATH!). However, it was an attempt. Even if it was the Feygrove Choker that could control vines for some reason, or the Winterclaw Owlbear dealing cold damage with its shriek using logic that escapes me, it was an ATTEMPT at making interesting monsters native to their environments. And that’s pretty damn cool.

Unfortunately, the idea fell out of fashion when 5e hit the scene. We still have variant monsters to fill roles (orc Eye of Gruumsh, Gnoll Pack Lord), but we lost the environmental beasts. Owlbears are, apparently, just owlbears, no matter where you go. And that’s honestly too bad, because 5e would have been a perfect time to take a serious approach to Darwinian evolution among monsters. Why? Because one of the core things about 5th edition that differentiates it from its predecessor is the fact that it’s a much more grounded game, thematically. Instead of a Winterclaw Owlbear, it would have probably just been given the “polar” descriptor. And that would have been pretty cool, wouldn’t it?

But they didn’t. So, instead, let ME show you how to do it for your own games.

But…Why?

Honestly, that’s a fair question. It would be easy, for example, to just re-skin any monster you encounter as its environmental variant. Want to fight a polar owlbear? It’s got white fur and feathers, now. Ta-da! Polar owlbear. Easy peasy.

But that’s the boring, shitty way to do this. Why?. For the answer, let me tell you a short story about an experience I had playing Fallout 4. No spoilers, I promise.

There I am, walking through the wasteland, Dogmeat at my side. Thus far, the experience I’ve had is a familiar one. I did, after all, play both Fallout 3 and New Vegas, so I know the game pretty well. Sure, there’s new crafting mechanics and some other interesting tidbits along the way, but it’s otherwise a pretty normal Fallout game. Me and my dog, wandering through the wasteland, fighting the occasional raider.

Then, for some reason, Dogmeat starts barking. Now, this happens occasionally. He’s a dog, after all. Then he growls. That normally only happens when there’s enemies about. I scan the area, see no enemy markers on my compass, chock it up to a glitch, and keep going. It’s a Bethesda game, after all. Suddenly, a bursting sound, like something exploding out of the ground, then I’m hit from behind. I turn around to see a nasty-looking mole rat lunging at me. I pull out my gun, which is of course my sniper rifle. Why would I be prepared for this situation? I switch, but it takes a while, so I back away from the nasty little beasty. Three more explosions, and now they’re coming at me from all sides. Finally, I have my shotgun. I take aim and fire both barrels. Two mole rats down, but I have to reload, taking hits the whole time. Dogmeat takes one of the others out, and I put a fistful of buckshot in the final monster.

Out loud, sitting in my chair outside of the game, I exclaim, “these things fucking BURROW, now?”

Shortly thereafter, upon finding an apparently-empty cabin, I learn that mole rats aren’t the only monsters that burrow, as a radscorpion jumps up out of the earth and beats the shit out of me. Even later, I find that mirelurks, as well, have started vacationing under the earth.

What the hell is going on!?

Now, the meta part of my brain understands this. Why do all of these monsters burrow? Well, mechanically, it’s so that you don’t have to deal with pop-in issues. The monsters won’t ever randomly spawn onto the map if they spawn underground and then emerge when you get close. And from a game design perspective, it’s a nice way to surprise players that would normally be tired of the humdrum of mole rats, mirelurks, and radscorpions of old. Suddenly, you effectively turn these monsters into a trap, just like a tripwire or proximity mine. It’s a neat idea.

But there’s more to it. Or, at least, my brain thinks there’s more to it. Because I immediately began trying to logic out the reasoning for their burrowing nature. Why in the hell are the radscorpions burrowing? Why are the MIRELURKS burrowing? In the logic of the game, what reason would these monsters that had previously been wandering targets suddenly have for becoming sub-terrestrial terrors? Well, it’s their environment, of course. Fallout 3 takes place in Washington DC. New Vegas takes place in the Mojave. Fallout 4? That’s Boston, Mass. What’s a major difference between DC, Vegas, and Boston? How about the stupidly cold winters? How about 4 times as much snowfall as DC on average?

What does this tell us? It tells us that the radioactive monstrosities of the commonwealth have evolved to suit this kind of environment. Sure, they’re still mole rats and mirelurks, but they’re also very different from their Capitol Wasteland or Mojave counterparts. They very likely hibernate during the winter, and have evolved to be lurkers, rather than hunters. They don’t track down prey, they wait for it to come to them, like spiders in a web. Why do mole rats seem to burrow in packs? Because it gives them a wider area for their tremorsense to detect.

And when I logicked this out, I suddenly had a greater appreciation for the whole design of the commonwealth as a campaign setting. It was similar, sure, to the previous wastelands I’d explored, but still had its little points of uniqueness that brought it to life in a way I hadn’t expected. And these mole rats that had seemingly evolved through natural selection were a huge part of that.

THAT is why you should take Darwinian monster design seriously. Because it’s one more way for you to draw players into your world and create something that they will remember.

How to Build Darwinian Monsters

First things first, you need to know how to build a monster. Got that? Then let’s proceed.

Building a Darwinian monster is done through two different methods: addition or reconstruction. Put simply, addition, is adding features onto a monster in order to adapt it, while reconstruction is pulling the monster apart and changing the way it works when you put it back together. Most Darwinian monsters are a bit of both. For instance, taking another gander at my Tropical Sahagin above, I added the poison damage and stealth bonuses, while I reconstructed it to lose the spear and speak with octopi instead of sharks. In order to use these methods, though, we need to go through our standard monster building process. And in order to illustrate the process, let’s actually build a Darwinian monster. In this case, let’s build our previously-mentioned Polar Owlbear.

The Monster’s Purpose

Let’s face facts. The whole reason to make Darwinian monsters is to subvert players’ expectations. If your players have never heard of a Spriggan, and you decide to include one in a desert landscape, nobody at your table is going to call you out on the fact that it’s in the improper environment. No one’s going to question it. That said, my desert treants are still going to be giant walking cacti, regardless of whether or not my players have watched Lord of the Rings. The point is that subverting your player’s expectations is not the purpose of the monster.

In the case of Darwinian monsters, you should probably look at the origin monster itself and do your best to determine what its original purpose is so that you can decide whether or not your variant will serve a similar role, or something different. Note that this is also where you determine the monster’s Challenge Rating. Is this new monster stronger than its cousins? Is it weaker? Why?

In the case of our Polar Owlbear, let’s take a look at the standard owlbear. They have RIDICULOUSLY low hit points for a Challenge 3 monster (59 puts them at Defensive CR ½), and have offensive statistics comparable to a Challenge 4 creature. In all honesty, the fact that they’re Challenge 3 instead of 2 probably speaks to the design aesthetic of 5e monsters on the whole (they tend to be a bit weaker than their challenge would indicate, based on the monster creation rules). This tells us that owlbears are brutes. They’re big, spiky damage machines built to hit hard. They don’t have a lot of staying power, but leave an impression when they do.

For my polar owlbear, I want it to have some more staying power. I want them to be a bit tougher. Thicker hide, more meat to take hits. Polar bears are like big white grizzlies, with thick layers of fat and fur to keep them warm in the cold. I want this to translate directly to more hit points and a higher AC. I also want them to control the battlefield a bit more than a standard owlbear. Normally, an owlbear is just a particularly scary monster that you find in the woods. Their polar cousins should feel a bit more cunning. So…a brutish controller type. And I think they should be a solid CR 4. These aren’t big badass bosses, but a strong enemy to set the tone in the second arc of a campaign. The kind of enemy that says “no more kid gloves.”

Traits, Powers, and Unique Features

This is where the real meat of making a Darwinian creature lies. Because this is where you get to decide just how different your monster is from its original form. In the case of the tropical sahuagin, determining its traits was a matter of me researching what features other tropical predators possessed. The consensus seemed to be “camouflage and venom.” Whether it was lionfish, sea anemones, or octopi, one or both of these things played a major part. I also had to decide if they were going to be able to control a different kind of creature. I decided that yes, they should, since I was going out of my way to change their nature by granting them camouflage and venom. I decided that octopi were sufficiently D&D-friendly while also fitting into the environment. All in all, a more traditional tropical sahuagin might control barracudas, but I wanted to change not only the sahuagin’s outward appearance, but also its tactics. Octopi, in D&D, are ambush predators, and I wanted this to translate. There aren’t tropical sahuagin raiding parties. They’re the highwaymen of the reefs; undersea pirates that go undetected until they swarm and destroy.

In terms of my polar owlbear, I want to look to two separate influences: the Polar Bear and the Snowy Owl. Unfortunately, there’s not much to learn from the snowy owl in terms of actual features and statistics. They’re opportunistic hunters that tend to nest in high places with good vantage of terrain. In terms of ecology, they’re interesting, since they tend to take other birds’ nests. But that doesn’t really help us with design. Polar bears, however, are much more helpful. For instance, polar bears are technically marine mammals, even though they are also land animals. This means that they’ll get a swim speed. They’re also quite agile, able to leap and maneuver on ice shelfs and across jagged planes of ice. In addition, their claws are short and stocky, designed for grip rather than hunting. This means that our owlbear is going to have a bit more dexterity than originally planned, and I think I’m going to give it a slam attack, rather than claws. This will also play into its battlefield control aspect, as it will be able to knock foes down with its slam attack. Finally, it should be noted that polar bears are stealth hunters, so some kind of bonus in their home environment is in order.

Putting it all Together

And here’s where it all comes together. Just like with a normal monster, we’re now going to fill in the blanks, plug in our numbers, and make our monster. And this should be the easy part, since you really did all of the hard, creative work in the other two steps. You already know how strong your monster is going to be, and where its statistics will generally lie based on its purpose. And you know what special traits and powers your monster will have. So now all you have to do is put it all together.

And this step becomes even easier since you’re already working from a template. In my case, all I have to do is modify the already-existing owlbear.

In the end, my monster looks like this:

What about yours? Share any Darwinian monster ideas you have in the comments.

Here are the PDF files for the Tropical Sahuagin and the Polar Owlbear:

Sahuagin

Owlbear