3 of the centipede’s tracheas continuously intake air while the other 5 expel it. Air flows through several layered folds inside the myriapod’s odd respiration organ. Unlike lungs, air flows in just one direction, with dedicated inlets and outlets. Not all of the tracheas are lined with runes, only 4 of the 5 outlets have them. From what I can tell, the runes are somehow propelling the gas passing through their respective outlets, generating a pressure gradient which allows for a continuous flow.

Thus, rather than alternating between inhaling and exhaling, the air is always moving in the same direction.

The walls of the tracheas are made of rigid chitin, as a sort of internal protrusion of their exoskeletons. The lines of the runes are composed of some sort of granular white solid, perhaps a Calcium salt.

All told, while the active respiration adaptations are clearly the reason these arthropods can grow to such sizes in an atmosphere with a normal partial pressure of oxygen, the airflow is decidedly weak. I can sense how much mana is flowing through their runes as well as how much air is being moved and I am not impressed.

In other words, the amount of air being pumped is, in my opinion, pathetic when you consider the rune’s mana consumption. Either this is an incredibly inefficient setup or using mana with runes to pump a fluid is simply difficult and/or impractical.

Regardless, once I learn how to make runes, I can copy this runic pattern for use in inorganic constructs.

Which brings up some interesting questions related to the origin of this species. If it is indeed artificial, then it could’ve been “engineered” to express these runes, which implies the designer understood its arcane effects. Furthermore, the designer would’ve needed advanced knowledge of biology; a level of understanding I wouldn’t’ve expected from the inhabitants of this world. So, either runic and biological knowledge was applied to the species, or runic knowledge is actually obtained from the observation of biology. Biomimicry, and all that.

It’s much to soon to jump to conclusions and assume they’re an artificial species. It’s equally possible the world’s civilizations discovered runes by observing naturally occurring biological arcane constructs.

Things like eyes, for example, are, arguably, considerably more complex than this, so I wouldn’t be too surprised if these runes did emerge via natural selection. You know what they say, evolution is a blind watchmaker. But that would imply runes could exhibit reducible complexity and maintain limited function, thus verifying the existence of quantifiable “physical laws” which govern magic. Exciting!

Moving on, I need to address my youngest minions. I have 200 of the little guys dashing through the undergrowth in the still-untamed cavern. The fact is, if I don’t intervene, most of them will become prey to other predators before they mature. I’m trying to establish a military force here; I should nourish the young centipedes.

I open one of my logistics tunnels up and will them to enter my dungeon proper. Essentially telling them to not harass my leafcutters and goliath2 beetles, I give them free reign. Additionally, I command any predators such as spiders, lizards, birds, squirrels, etc. to leave them alone.

I’m not going to lie, my main dungeon areas probably won’t be able to sustain 200 fully grown cave centipedes, but it’s a good enough nursery for now. I can send them back out into the cavern once they’re big enough to fend for themselves, and by that time, I’ll probably have full control over its animals anyway.

It’s time to get serious about my safety, while having powerful predators under my influence is essential, expansion is equally important. My dungeon helpers are absolutely instrumental in facilitating my growth. The more I grow, the more minions I can support, as such, expanding goes hand-in-hand with defense.

While my normal dungeon helpers are useful, and will always remain as such, there are some tasks which would be simpler if I had a larger caste available.

I could take the hard route and try to splice red blood cells and their dependencies onto ants, but why go through the effort now that I have access to arthropods who already express the adaptations?

Sure, myriapods and insects aren’t nearly as closely related as you’d initially assume, but by golly, they’re closer than vertebrates!

Not only will I need to change the nature of the ant’s blood, but also their circulatory structure… In fact, there’s even more to it than that; red blood cells don’t contain nuclei and are thus incapable of cellular division. The centipedes bypass this difficulty by having a small marrow containing cavity in their bodies which produces red blood cells.

Already, I can tell this’ll be challenging, and I haven’t even considered the gas-exchange organ. It’ll no doubt require multiple passes.

Before I initiate the modification process on one of the queen ants, I gather up 14 magicite crystals, my entire collection, around my dungeon core. Topping off their mana reserves, I set them in place around me. My intention is to draw mana from them, in addition to my innate reserve, while I make the modifications, hopefully saving me some time.

I begin the familiar process of wrapping my sense around an organism and begin mentally forming a new template.

…

Geez, that was an ordeal. I’m almost embarrassed to say it took me 24 hours of intense focus to establish the modification template. After that, I poured every last bit of mana I could spare into the modification, and I can already tell it will take a couple more attempts before I’m finished with the circulatory system.

Which is crazy, really, with the cavern and all the other latest additions to my dungeon, I have a veritable ocean of mana at my fingertips. My internal mana capacity has scaled proportionally to my regeneration rate, so it’ll only take a little over a day to reach my maximum capacity again. Still, it’s insane how much mana this is going to require! And I still have yet to include the respiratory organs and size boost!

Really, there’s no reason for me not to go ahead and include those changes in the template, so get to work on that while I wait for my mana to fully regenerate.

…

After 30 hours my mana has fully replenished, in that time I had almost, but not quite, finished the new template. I had to take some, uh, creative liberties with the placement of the tracheas. Or more accurately, I reduced it to 1 inlet and two outlets, with the rune-bound one being the (significantly) larger of the two outlets. I’m not entirely sure why only some of the outlets had runes, perhaps they serve some sort of pressure equalization purpose which is useful in the event of a blockage. Who knows? In any case, I figured I should include them since I don’t understand their function and they might play a vital role. More research is needed. More research is always needed.

Once more, I begin pouring mana into the target queen.

…

Three more iterations, three! In total, I’ve sunk 6 days into this project.

Well no, I finished the template a day ago, but I had to perform some long overdue gardening and dungeon micromanagement in the meantime. I just hope it’s all been worth it…

If everything goes well, the final version should be a staggering 50 centimeters in length! Based on my observations of the diminishing returns associated with the mana expenditure and the degree of change, I can safely conclude that I am far from the new size limit, but I’m going to need a lot more mana for that...

Actually, here’s something interesting: before I had access to Advanced Arthropod Respiration™, I was unable to make my ants any larger. At first, I thought this was due to some sort of limitation on how much I could change something, but in these past few days I’ve managed to achieve something way beyond my initial expectations. Perhaps that’s a result of the growth in my mana reserve and/or practice.

When working on a template, I can somehow tell whether or not a modification will work, for instance, if I remove a species' heart, I have an innate sense that it will result in a miscarriage. Does this mean my subconscious is simulating a living being, or is it just an instinctive layer of common sense? Probably the latter.

Dungeon core psychology is a right mystery, I feel that if I keep questioning these things, I’ll be opening Pandora’s Box.

And you know me, I definitely wouldn’t leave such an intriguing mystery untouched. Yet another thing to add to my official List of Things to Look Into Once Safe.

Anyway, my new caste of leafcutters if complete. Just as before, I instruct the modified queen to produce some new haploid alates, virgin queens and drones, so that I may have multiple of the modified queens in the future, for insurance purposes of course.

Flexing my mighty creative talents, I come up with a brilliant name for the new variant: Super Helpers. These fellas are going to be huge, the brood chambers definitely won’t be large enough, so I set to work manually excavating a new set of chambers for the main leafcutter nest to expand to. After all, I can’t rely on the ant’s natural instincts to accommodate their modified brethren, so I have to dig their specialized housing myself.

…

After just a couple hours, I’ve carved several sprawling leafcutter warrens suitable for half-a-meter worker ants. I don’t know how much food these individuals will need, so I instruct the queen to lay more eggs than is probably sustainable, 500 to be exact. If that ends up being too many, and it most certainly will, then I can feed the excess to my little centipedes.

Well, they’re not very little anymore. After 6 days of engineering my monstrous ants, the energetic predators have molted several times and grown substantially. At 25 centimeters long, they’re already the strongest of my current species, and they’re still just a 4th of their adult size! It won’t be long before every species in the cavern comes under my control. Indeed, other than the dragonflies, certain vipers, and some plants and fungi, I already have total control. Here’s what Mr. Normal had to say about that:

It’s still odd that I get separate entries for the same species. These fungus gnats are quite interesting, being fully adapted to cavern life. Much like the giant cave centipedes, they sport rune-assisted “lungs.” This would’ve been an excellent opportunity to prove whether or not giant arthropods were engineered if only the differences weren’t substantial.

Unfortunately, (Or fortunately, from another perspective.) their respiratory system is different enough from the centipede’s that I can’t conclude they’re artificial. The fungus gnat adults have 66 small pores on their bodies while the maggots have 48. Each pore has the same runes as the cave centipedes and is isolated from the other pores, not forming a network. Every few seconds a fly (or maggot) “exhales” by cycling a pulse of mana through the runes in each pore. The pores each expel some of the air inside them, and the resulting low-pressure area causes fresh air to rush back in after each cycle. Not at all like the continuous unidirectional flow of the centipedes.

Now that I think about it, this is a method which seems much more suited to species like flies (Or ants…) who have a larval stage, as opposed to species like centipedes who’s young are essentially smaller adults. Too bad I’d created the super helpers before making this discovery.

Moving on, their larva are glow worms who produce long silken “fishing lines” out of saliva on the cavern’s ceiling. At 40 centimeters long, one worm can apparently create about 30 lines, some of which can be as long as 10 m! The glow worms emit a soft blue bioluminescent light, which serves to attract prey to their nests. When flying animals get tangled up in their dangling lines, the worm will reel them in and devour them alive. I’ve seen many cave swallows meet their ends in these traps. In fact, the only escapees I’ve witnessed so far have been the enormous dragonflies.