Size of Monsters

In order to fulfill some of our patron's unit requests, I've had to begin statting out the sizes, carrying capacity, and other characteristics of very large creatures - rocs, dinosaurs, etc.


Since in my game designs I always try to be as grounded as possible, the formula I use to assess the value of an animal includes a factor for carrying capacity and a factor for years to maturity, both of which are impacted by physiological factors such as muscle mass and body form. This was easy for horses and camels. I wanted to bring a similar level of empirical study to the more fantastical creatures.

I decided to review the scientific literature to see what could be learned. "How much can an eagle carry? That might influence how much a roc can carry." I was of course familiar with the square-cube law, which states that as size increases, mass increases at a faster rate, imposing a limit on maximum size. And I was familiar with the idea that large animals can't fly because their muscles can't generate enough lift. So I knew a roc couldn't be "real".


What I didn't realize is that scientists have no real idea how dinosaurs or prehistoric eagles could be "real" either!


Consider Angelos C. Economis article on "The largest land mammal", where he demonstrates that a land animal cannot be larger than 20,000 kg:

That's interesting, because we have fossil records of dinosaurs five times as large.


Ah, you say! It's because big dinosaurs are amphibious - they live in swamps where the water would help support their weight. The problem is that the big dinosaurs show all the hallmarks of being terrestrial, not amphibious, and their fossils have never been found in swamps. Robert Bakker convincingly showed that dinosaurs weren't amphibious at all. But to this day, it's not clear how they supported their weight, pumped blood, or lifted their heads. (As the literature puts it, "dinosaur biometrics are not well understood." When a scientist says "not well understood", he means "baffling anomalies".)


It gets wierder. The largest birds today is the wandering albatross. It's so large that it can hardly fly, and it's generally considered to be at the upper limit of powered flight by birds. For centuries, eagle breeders have been trying to breed larger and larger eagles. They've never gotten them bigger than 25-30lbs. So what does one make of Argentavis Magnificens, a 150lb bird with a 7m wingspan?


Or, even more interestingly, what do we make of Quetzalcoatlus, who some experts think might have reached 15m in wingspan and 450kg in weight?


The scientific literature is beside itself over Quetzalcoatlus. Some scientists argue that it must have only weighed 70kg in order to fly - which physiologists then claim is far too skinny, as the creature is the size of a 1,000kg giraffe.


Others claim the creature must have weighed 450kg, and that it couldn't fly - even though everything about its body build, frame, wing span, and other characteristics suggest it *could*. So they more-or-less split the difference, call it 250kg, and say it could fly long enough to glide.


I won't even begin to get into the fact that dinosaurs like T-Rex were bipedal, and show some evidence for adaptions that would have let them *jump*, or the fact that there may have been pterosaurs larger than Quetzalcoatlus, or dinosaurs bigger than Brachiosaurus.


All of which is a very long way of explaining why, ultimately, I think I'm ok with the fact that rocs can fly, and dragons can be huge and fast, even though I can't explain how. If you ask me, I'm going to say "the flight mechanics of rocs are not well understood" and "the biometrics of dragons are not well understood".

My pet theory is differences in atmospheric density and oxygen content; higher density would buy you more lift on avians, and higher O2 would let you scale up bodymass.

Unwin and Habib’s work on Pterosaur flight is fascinating stuff - their outward estimates say that the Quetzalcoatlus northropi could have flown 80 miles an hour for seven to ten days, topping out at a maximum range of 8,000 to 12,000 miles.

One of their more fascinating observations is that Q. northropi should have been capable of takeoff from flat earth while standing still in about a second.

Other folks disagree with them, but what they say is plausible. They have solid refutations of counterarguments.

for those who aren’t interested in scientific journals, there’s a great NPR piece on it:

All of that is to say that, yes, the doubled speed of travel for fliers should be taken seriously. And they should decidedly be able to “force march” right over an ocean if needs must.

Mmm I think you have missed the core question which is “what is the airspeed velocity of an unladen swallow”?

All right, here is the communities' opportunity to shape the game! A few monsters could have sizes that wildly vary, depending on one's assumptions about the nature of the creature. 

For each monster below, I offer a variety of "body types". Different body types have different sizes and masses per HD. For instance, Lions have less mass per HD than Bears; Elephants have more mass per HD than Bears. Put another way, different body types have a varying degree of killing power per unit of weight.

Because of the square-cube law, small differences in  length add up to big differences in mass. Big differences in mass add up to huge differences in wingspan (for flyers).

Basilisk: built like a Komodo Dragon (10' long, 300lb); built like a Crocodile (20' long, 3,000lb); or in-between (13' long, 633lb)

Huge Venerable Dragon: built like a Pteranodon (23' long, 85' wingspan, 1450lb); built like a Crocodile (80' long, 235' wingspan, 43,500lb); or in-between (41' long, 120' wingspan, 4,500lb).

5-Headed Hydra: built like a Komodo Dragon (7' long, 200lb); built like a Crocodile (16' long, 2,300lb); or in-between (12' long, 450lb)

Giant Roc: built like an Eagle (47' long, 140' wingspan, 4,500lb); built like a T-Rex (83' long, 250' wingspan, 28,000lb); or in-between (70' long, 203' wingspan, 15,000lb)

There's no "right" answer, merely different conceptions. How big do you imagine a Roc? how big do you imagine a Huge Venerable Dragon (22HD)? etc.


APM: Basilisk: built like a Komodo Dragon (10’ long, 300lb); built like a Crocodile (20’ long, 3,000lb); or in-between (13’ long, 633lb)

Built like a crocodile (20’ long, 3,000lb).

APM: Huge Venerable Dragon: built like a Pteranodon (23’ long, 85’ wingspan, 1450lb); built like a Crocodile (80’ long, 235’ wingspan, 43,500lb); or in-between (41’ long, 120’ wingspan, 4,500lb).

I imagine Smaug from the Hobbit film with that enormous tail slipping into Erobor . 80’ Long, 235’ wingspan, 43,500lb. Like horrific, blot out the sun when it’s in the sky force of nature sort of big.

APM: 5-Headed Hydra: built like a Komodo Dragon (7’ long, 200lb); built like a Crocodile (16’ long, 2,300lb); or in-between (12’ long, 450lb)

Crocodile (16’ long, 2,300lb) or larger, like 20’ long and about 3,000lb.

APM: Giant Roc: built like an Eagle (47’ long, 140’ wingspan, 4,500lb); built like a T-Rex (83’ long, 250’ wingspan, 28,000lb); or in-between (70’ long, 203’ wingspan, 15,000lb)

In-between (70’ long, 203’ wingspan, 15,000lb) - the huge ancient dragon should outshine the roc.


Basilisk: Komodo Dragon. I’ve always thought of them more Squamata than Crocodilia.

Huge Venerable Dragon: As big as possible: Crocodile. I’ll almost always default to more real world norms, but dragons are elemental forces, infused with the magic of the world. They should never stop growing.

5-Headed Hydra: Crocodile. There’s a lot of chest in this monster, big muscles to move all those heads around, lots of shoulder/spinal structure to support the weight. There’s gotta be room for head buds (like teeth buds) in there too. (and holy moly, hydra head buds are my new favorite monster part)

Giant Roc: I’m gonna go with Eagle size as long as that’s big enough to pick up and fly off with a heavy warhouse with rider. If not, size it until it is - that’s my mind’s eye of a Roc. It’s main competitor for food should be equivalent sized dragons.

There’s a better world where Plains Indians had to occasionally go to ground during a buffalo hunt while a Roc got it’s first pick.

Basilisk: Don’t care.

Huge Venerable Red Dragon: As big as the D&D Icons Colossal Red Dragon “miniature” I keep in my closet to haunt my players’ dreams.

5-Headed Hydra: Python, not crocodile. I like my hydras serpentine.

Giant Roc: In between, so I can say “It’s wingspan is about the same as a 747.”

Basilisk: Komodo
Venerable dragon: crocodile or larger.
Hydra: tending toward crocodile based on length, but I tend to agree with James on serpentine hydras
Giant roc: varies with the depiction; I’ve seen art for them carrying things as large as elephants or whales, or as small as horses. Not really sure.

I change my answer on Hydra to that one - Serpentine. On a lark I did a GIS for “Harryhausen Hydra” and just realized that’s what’s been in my brain for 20+ years.

I think I keep conflating the body type with Tiamat.

Basilisk: Komodo

Huge Venerable Dragon: as big as possible; uniquely, terrifyingly big

5-Headed Hydra: Crocodile, but I also like the serpentine idea

Giant Roc: not sure; aren’t Rocs from 1001 Arabian Nights? I would try to “size” them based on what they did in the original source material.

In the original source material, Rocs are described as (a) having a wingspan of 48 (by Marco Polo)'; (b) having a wingspan broad enough to block out the sun; (c) having feathers 8 yards long each; (d) having feathers the size of palm fronds; (e) being capable of picking up an elephant. So the sources are not highly consistent.

The Giant Roc, in ACKS, has 36 HD and deals the same damage as a 22HD dragon. Right now I have it as 205' in wingspan and capable of carrying 6,000lbs (a small Asian elephant).

The Small Roc has a 44' wingspan, and would thus be the one that Marco Polo "saw".



From your explanations, I’d say the current Giant Roc and Small Roc are perfectly sized. My answer to the original question on the Giant Roc is “in-between” to most closely match the current size.

Basilisk: Komodo

Huge Venerable Dragon: as huge as possible. Wouldnt mind if the Giant Roc had a bigger wingspan though.

5-Headed Hydra: Serpentine sounds like an interesting idea! Makes them more distinct then just being “A dragon with many heads”

Giant Roc: 205’ for a wingspan sounds great!

Basilisk - Komodo

Huge Venerable Dragon - Bigger than anything else on the world except an even bigger Huge Venerable Dragon. I’m more inclined to say that the biggest dragon should be pitching at 200’ long which ridiculously large. This: more than anything else.

5-Headed Hydra - This big:

Giant Roc - In between sounds about right.

I'm really glad I brought these questions up. You all have steered me in a radically different direction than I was going.

My original plans were to make dragons and rocs substantially smaller - building them as more realistic flying creatures. The largest dragon had about a 48' wingspan, I think, and the largest roc about 60'.

I've now updated my formulas and as a result the Hugest Venerable Dragon is is 95'' long with a 30' tail, with a 280' wingspan. It is moreless as long as a football field is wide, and its wingspan is the length of a football field.

It's not quite as big as in the awe-inspiring image that James shared above, but it's large enough that its bigger than the width of a typical keep, and its wingspan is greater than the two wall segments. It's as long as a trireme. 

I could make it bigger, but it's ultimately a 26-HD monster, and there should be some correlation between size and hit dice.




So it’s about as long as the largest complete Diplodocus found so far. “The longest complete dinosaur is the 27-meter (89 ft) long Diplodocus, which was discovered in Wyoming in the United States and displayed in Pittsburgh’s Carnegie Natural History Museum in 1907.”

That’s pretty cool, and gives us something real we can measure against :slight_smile:

I think it’s also worth remembering (for me at least) that this is basically the ‘biggest’ dragon that there could be, and younger ones that haven’t got the huge size attribute are going to be substantially smaller - but even an adult dragon should be terrifying.

*95 FEET long, not inches

Now I’m imagining a buffed-up, magic-item-equipped, level 14 fighter charging a football-field sized dragon. Definitely the stuff of epic fantasy, if not necessarily as realistic as ACKS normally is (that is until the fighter gets eaten).