Crabs and Crablike Non-Crabs

Not too long ago I came across a bizarre natural phenomenon called “carcinization” that had become a bit of a meme. In brief, it’s the tendency of evolution to converge on the form of crabs, something that has occurred at least five times in earth’s recent history. My mind, functioning as it does, began to wonder what this phenomenon would look like when applied to a fantasy creature, and it doesn’t get much more fantasy than dragons! No one asked for this, but here it is just the same, an exploration of the hypothetical evolution of the “Crab Dragon.”

This exploration begins with examining the morphology, the essential form, of crabs. Naturally their claws stand out, and their hard carapaces. I learned that beyond eating, their claws are used to communicate with each other. Crabs are surprisingly social and cooperative.

These traits combine to make crabs into very successful omnivores, of which there are over 850 “true” species, but this article isn’t about crabs. It’s really about crabs that aren’t actually crabs, and it’s really not even about them; because they’re mostly just lobsters that tucked their tails. This is about the majestic crab dragon!

Dragons

Dragons in the modern fantasy tradition are basically fire-breathing brontosauruses with wings, and they are very cool creatures, but they are by no means crabs. Thankfully this can be remedied through the magic of totally made up evolution! So first let’s talk about the environmental factors that I believe give us the best chance at getting crab dragons, caves!

That’s right, the very same places dragons like to keep their treasure hoards are what I believe to be the prime conditions for evolving our draco-crustaceans. Dragons, as it turns out, are poorly evolved for caves. They have all the traits of super-lethal airborne ambush predators, and like the real life raptors that share those traits, dragons should be perched up high; with open sky above and wide swaths of land filled with hapless, juicy peasants below. 

Alas caves, we are told, are where dragons spend a good deal of their time. Sad for the poor dragons that should be soaring through the air, but excellent news for game designers with a proclivity for fantasy carcinization.

Crab Dragons

Dragons that evolve to suit a subterranean environment might as well take on the traits of crabs for a number of reasons:

1. Those wings aren’t getting any use underground, giant freaking claws though? Those can dig, and grab food; way better.

2. Long tails are a liability underground, they are gonna get snagged on stuff when the dragon is trying to turn around in the tight spaces. Don’t believe me? Check out these other subterranean champs: moles, badgers, prairie dogs. No tails there! Crabs figured this one out too, they tuck their tails under their tummies.

3. Technically this one doesn’t have to change, but there’s no way I’m letting Crab Dragons get out of this without creepy crab mouths.

4. Those front facing eyes only look in one direction, and crab dragons don’t have time to be turning around to look behind them all the time. Crab eyes are up on stalks and have a broader field of view.

5. Who needs feet when you could have big chitinous spikes that cling perfectly to the spaces between stones? Also crab dragon legs sound delish. The world needs crab drangoon. This whole article might have been written to set up that pun.

The Wings

So first stop is the wings, they gotta turn into claws, and I think there’s a pretty reasonable way to explain how that could happen. When a dragon is underground those wings aren’t getting used for flying, but their bat-like wings have those handy thumbs on the tops of them. I bet those thumbs get used to manipulate rocks and treasure all the time.

Given enough time and natural selection, you’re going to see subterranean dragons with tougher, thicker thumbs that are better for digging around. Meanwhile those delicate elongated fingers are spending all their time folded up and going to waste, but we’ve got a plan for those too.

Eventually those fingers are going to shorten and eventually fuse together, because it stands to reason having shorter stockier wings is going to be less of a liability than sweeping, delicate ones. You can see glimpses of this evolutionary trend in flightless birds. So everything is getting thicker and shorter as the draglodytes use their wings more and more as arms rather than wings.

Many many years pass, or some really freaky magic, and eventually the forearm and fingers have totally fused into two long, solid bones. The top bone is fixed, just like the top of a crab claw, and the bottom bone is jointed at the elbow to help the dragon pick things up, or crush them to death.

The Tail

Graceful and elegant though they may be, dragon tails just get in the way in a cave. There is a solution, however, because the genius of the crab’s form knows no bounds. It might not look like it, but crabs do have tails, they just tuck them underneath their bellies. Interestingly their tails are sexually dimorphic as well; with female crabs having a larger one for carrying eggs. This is one of the crab’s defining characteristics.

Tails are enough of a liability under ground that eventually nature would select for shorter and shorter ones, but if the dragon plays its cards right, it could maintain the tail and gain a whole lot of utility. Over time tails tucked under the dragon’s comparatively soft belly would begin to broaden, because the broader the tail the more protection it grants, and those dragons would go on to make more baby dragons.

Moreover, while we’re on the subject of crab dragon procreation, a broad tail capable of holding a clutch of eggs to the dragon’s chest protects their offspring from pesky adventurers that would steal them for profit or kill them to satisfy a quest. Clearly dragons should have crab-like tails, it’s a wonder they don’t already.

The Rest

The remaining evolutions (devolutions) that I think belong on crab dragons are really only included here to satisfy my malign sense of humor and love of the absurd. So I lump them all together here.

Dragons with crab eyes look ridiculous, and I love it so much they must be part of this horrible monstrosity. I don’t actually think crab eyes are better suited to them, plenty of subterranean animals make do with regular socketed eyes, so I can’t actually imagine conditions that would cause them to evolve. But I want them there, so that will just have to be enough for you, dear reader.

Something similar can be said about giving the crab dragon spiky crab feet. A dragon’s natural clawed toes are arguably superior for a number of reasons. Superior in many ways except for one, long spikes on the ends of a dragons legs are terrifying, and I so want to see one of my player characters impaled by a stampeding crab dragon that they spooked.

Finally the mouth. I loosely justify giving crab dragons a more crablike form thusly, a big lower jaw is going to make it hard to get food from the claws to the mouth. A beak would work, but this article isn’t about squid dragons, that would be absurd. So the bifurcated mandibles of crab fame are affixed to our dragon’s lower face. At this point I feel bad for the poor creatures, and I think this is enough.

Conclusion

I set out on this little mental adventure for a couple of reasons. Mostly I think it’s funny as hell, but the secondary, and more practical reason, is that thought experiments like these can be really handy for game designers and storytellers in general. A bizarre variant of a favorite monster can add a really fun twist to a game. Monsters that appear to have forms adapted to suit their environments feel more alive and believable on an intuitive level. Will crab dragons ever be a thing? Probably not, but it was fun to talk about them anyway.

The following is a 5e D&D monster template written by Michael O. Varhola that can be applied to any dragon.

Crab Dragon

Whether spawned in nameless netherworlds, bred in the seaside laboratories of insane wizards, or created by mad gods themselves, Crab Dragons comprise all of the most powerful physical characteristics of their draconic and crustacean forebears. They do not have the same intellectual legendary capabilities of conventional Dragons, however, and are somewhat impeded in this regard by their Crab ancestry. 

Over-Armored: Crab Dragons combine the impressive defensive characteristics of both sorts of creatures that compose them, the resulting great plates of chitonous scale protecting them even more than would be the case for either constituent creature. This slows their overland movement somewhat, however, and their flying speed substantially. 

Deliciously Deadly: While Crab Dragons do not have any natural enemies — largely because they are pretty unnatural creatures — their deliciousness is unparalleled and legendary. This might prompt wealthy patrons to commission adventurers to obtain Wyrmling or Young Crab Dragons so that they might be served at lavish banquets, or for powerful beings like Giants to hunt even larger ones for their most epic feasts. Those of different colors have various nuances to their flavor (e.g., Black Crab Dragons taste like they have been infused with lime, Red Crab Dragons are inherently spicy, White Crab Dragons are ideal for chilled dishes). 

Such great monsters have ample means to defend themselves, however, to include slamming enemies with their armored forelegs, chopping them up with their powerful claw-wings, and biting them with their under-developed Crab-like mouths. 

Absurdly Unfrightful: Despite their great size and power, Crab Dragons have a somewhat ungainly and ridiculous appearance and much less force of personality than do pure-blooded Dragons and do not have a frightful presence. Their composite physiognomy also makes legendary actions associated with true Dragons impossible for them. 

Crab Dragon Template

When a Dragon has been crossed with a Crab by whatever means, its type remains Dragon but some of its other statistics for the base Wyrmling, Young, Adult, or Ancient creature should be adjusted as described below. It might retain or lose any or all of its lair actions or inherit new ones altogether, as the storyteller sees fit. 

Armor Class: Increase by +3. 

Speed: Decrease walking speed by 10 feet, decrease flying speed to half, and add swimming speed of 30 feet for Wyrmlings and 40 feet for all other ages. 

Challenge: Reduce by 1 for Wyrmling, 2 for Young, 3 for Adult, and 4 for Ancient. 

Ability Scores: Reduce Intelligence and Wisdom each by 2 and reduce Charisma by 4. 

Frightful Presence: A Crab Dragon does not have this special trait. 

Multiattack: A Young, Adult, or Ancient Crab Dragon makes three attacks, one with its bite, one with its claws, and one with its forelegs. 

Bite: Reduce bite damage from d10s to d6s (e.g., 1d6+2 rather than 1d10+2 for a Wyrmling Black Crab Dragon, 2d6+10 for an Ancient Red Crab Dragon). 

Claw: Increase claw damage from d6s to d8s (e.g., 2d8+5 rather than 2d6+5 for a Young Blue Crab Dragon). 

Foreleg Slam: Attacks with a Crab Dragon’s blunt forelegs inflict 2d6 + Strength bonus bludgeoning damage. 

Legendary Actions: Crab Dragons do not receive Legendary Actions. 

Variant: Underwater Breath Weapons

Under normal conditions, Crab Dragon breath weapons function just like those of normal Dragons, but when used completely underwater their effects might manifest somewhat differently. 

Acid: Lines become cones that are two-thirds as long but with acid that is diluted and which therefore inflict d6s rather than d8s (e.g., an Adult Black Crab Dragon underwater breathes a cone of acid that is 40 rather than 60 feet long and which inflicts 12d6 rather than 12d8 damage). 

Cold: Cones are two-thirds as long but turn to ice, causing creatures who fail their saving throws to become trapped within them. A trapped creature may attempt a Strength saving throw each round to escape, with the same DC as for the breath weapon, and failing it may begin to suffer from suffocation (i.e., Water Breathing will not allow intake of oxygen through solid ice). Furthermore, ice not fused to solid objects will float upward until it reaches the surface or something that blocks its movement, carrying anything trapped within it. 

Fire: Fire mixed with water turns to steam but does not have any different mechanical effects. 

Lightning: Lines are half as long but twice as wide as the electricity discharges into the water (e.g., an Adult Blue Crab Dragon underwater exhales a line of lightning that is 45 rather than 90 feet long but which is 10 feet rather than 5 feet wide). 

Poison: Unaffected.