One of the important differences between inhabitants and ecological creatures is the precision and power available to evolving inhabitants.

Mordecai's experimentation with incorporating stronger metals into the hard structures of mundane creatures laid the groundwork for his changes to some of their existing inhabitants as well as the new inhabitants upgraded from some of their ecological occupants.

He'd already established the template for upgrading river drakes to brine dragons, complete with breath weapons and water-based magic, but instead of gaining electric powers to make them eletsima dragons like Nezha and Ysi, he enhanced their scales, bones, claws, and fangs with a latticework of the new metals, though he adjusted the exact structure and mix to create different visual effects.

Their scales obtained a rainbow sheen that shifted with the angle of the observer. Claws and teeth shone with a slightly reflective metallic gleam that held a hint of pale blue in its silvery hue. Their bones, for those who might ever end up seeing them, were now a dull black from the dense metal that infused them. Mordecai added a final, invisible tweak that he'd learned from one of the samples: all of these were impregnated with microscopic flecks of diamond crystals.

Even magical weapons would have difficulty maintaining an edge after striking those scales or claws. Some enchantments were strong enough of course, but they were relatively rare.

This would make the hardened alloy weapons available as rewards even more valuable. Without the need to combine them with lots of carbon, it was much easier to keep the weapon and armor rewards from being brittle when hardened with the new metals.

For the crabbits and swamp drakes who were ready to migrate to a stronger zone, Mordecai gave the same upgrades to their hard tissues, with the exoskeletons of the crabbits obtaining the same sheen as the upgraded scales did.

The swamp drakes needed minimal changes to turn them into bottom-dwelling creatures that could hide in the mud and sand at the bottom of the sea. They also maintained the flexibility to swim up to the surface and use their claws to climb onto ships.

However, the crabbits needed a little more alteration. Crabs were never great swimmers to begin with, but the crabbits were really bad. So he went with giving them a small surprise instead. If they crouched down to make a jump like their swamp selves, the action also primed a powerful jet of water. They might not be able to swim properly very well, but this maneuver could catch someone trying to escape. As a final bonus, Mordecai didn't have to do anything with their 'scream', the unearthly harmonies would be amplified simply by being underwater where everything was louder. This applied to the shock waves of their hydraulic-powered punches as well.

When the king otters grew strong enough, they could migrate down with a simple increase in size, tougher hair impregnated with metal, and saltwater adaptations. The dungeon still only had the initial pair as adults, plus their young ones.

While the bunyips were also few in number, they did have a trickle of dire rabbits interested in the upgrade, so the saltwater adaptation was an easy minor upgrade. They weren't very strong combatants to begin with, so they retained the roles of rescuer and healer for the most part. Mordecai gave them the option of participating in combat as support for the inhabitants, but with the restriction that they had to wear a scary mask with some matching costumery to designate them as combatants, separate from the normally non-combat bunyips. He didn't want there to be any mix ups when bunyips were trying to help delvers in trouble.

Mordecai created an upgrade template for the giant axolotls as well, granting them saltwater adaptations and toughing their skin and bones. They would not receive a size upgrade; instead, they were given the ability to adjust their skin's color and texture to provide deep camouflage.

The final current species of inhabitant to receive an ocean upgrade was the pixies. Their flighty nature made it harder to nail down what they truly wanted instead of what was simply an interest of the moment, so Mordecai created the upgrade template with a requirement for a pixie to acquire it; they needed to have both a strong enough will and spirit, plus enough focus and resolve to ensure that it was a real desire.

The upgrade itself was simple enough. It gave them a 'mermaid' form that retained their wings, though the wings now looked almost like flying fish fins rendered iridescent by fey magic and a faint trace of one of the new metals. They could transform between mermaid and normal pixie form but retained the new style wings. Mordecai didn't touch their 'flower' transformation ability, but neither he nor Kazue were particularly surprised when they started adapting themselves to the ocean environment.

Sea anemones were the first flower-like form that was adapted to, despite them actually being animals. This trend towards taking on minor animal forms instead of plant forms continued with other bottom-dwelling but visually spectacular species like starfish and sea urchins.

They also had some options on the scale patterns of their new fishtails. Many of them enjoyed the rainbow sheen Mordecai had made common, but some also wanted other metallic patterns such as the wavy pattern common to certain methods of folding high and low-carbon steels. A few of those wanted the same pattern but in precious metal colors, such as silver and copper or silver and gold.

As a final touch, this was the first new form for the pixies and thus their first upgrade in power. This was reflected in their size; those with the mermaid upgrade were now at least a foot tall in either normal or mermaid form. This wasn't really a choice but a natural reflection of increased power. There were few paths of increasing power that left tiny fey creatures at their original size.

After that, it was time to induce some new inhabitants from amongst their ecological creatures. He began by setting up a rule to automatically apply to all of them: ensuring that they could breathe both air and water. It was the simplest way to leave a lot of options open.

Mordecai wasn't looking to make these immediately strong, instead, he wanted to make these new species have a slow growth pattern that would let them eventually become huge, but for now, they would start at smaller sizes in a 'juvenile' form.

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The first of these were crabs.

While there was some overlap with the crabbits, these were almost normal crabs in form and function, though their carapace was hardened and reinforced the same way as other ocean creatures in this zone.

The metallic crabs would start at about twenty pounds in weight, which was within the range of some species of normal crabs, and would act as ground support when delvers were dealing with swimming inhabitants.

However, they would slowly grow from there and after several decades they would be the size of a small elephant, weighing in at three to four tons. They were starting well below the power cap of this zone, and that cap would go up for quite a while given the current growth pattern for their territory.

The 'up' and 'out' zone sets still needed some rebalancing, but that work needed to wait until they did their next 'out' zone.

For ranged support, Mordecai went with evolving sea urchins into giant forms that could fire off their black metallic spines. They wouldn't move fast, but they were well-armored and able to shift the position of their spines by flexing, making them difficult to bypass. But just firing foot-long plus metal needles was a little boring, so he spiced them up by giving the fired needles a random chance to have other properties.

On impact, they could unleash an electric discharge, a cloud of acid or poison, a burst of super-heated steam, or instantly freeze the area around them. Only about one in ten fired needles would do this, and the urchin had no control over which ones would be enhanced or what the enchantment would be.

Given how fast they could fire their needles, this was still enough to make combat with them quite intense and interesting.

Next came the fish. Or at least, fish-like creatures, given Mordecai's designs.

As they were going to be starting off relatively small, he decided they should also act as an aggressive school of fish, no matter which variety they were. As they grew larger, they would spread out and tend to become solo hunters. The schools wouldn't have more than twenty members, which could still be an overwhelming number when they were all ten or more pounds each.

One of the stranger-looking ones Mordecai created was the turtle-sharks. The base body shape was that of a shark, but much of it was covered in a thick, hard shell like a turtle. They could also stretch out and bend their necks, which normal sharks could not do. Doing so created some gaps in their neck armor, so most of the time they had their heads drawn in tight, which made them look more like normal sharks. They were slower than most sharks their size, but it was much harder to damage them.

Razorfin sharks were going to be the fast attackers of the set. While they had hard sharp teeth and a sufficiently strong bite, their primary attack was going to be to run into and slide along their targets. Not only were the edges of their fins as sharp and hard as their name implied, but they also had sharp, raised ridges running down their long, thin bodies.

Evolving some fish into rays was a bit trickier than making shark-like creatures, but far from impossible. These he gave long tails with poisonous stingers, plus the ability to shoot either pressurized balls of water that would explode upon impact or high-pressure streams of water to knock people away. He also gave them the ability to launch from the water into the air and maintain flight indefinitely.

Freshwater eels were fairly easy to evolve into giant electric eels adapted for salt water. But even with strong jaws, that felt insufficient, so Mordecai also gave them snake-like muscles and flexibility, allowing them to wrap around prey and constrict them while giving off the occasional electric discharge.

After finishing with his fish-like creatures, Mordecai moved on to a couple of soft-bodied creatures.

The first one was technically related to slugs, though its translucent and delicate appearance had earned it the name of 'sea angel'. The normal version of such creatures didn't generally make much noise, but these ones Mordecai gave the power to sing in the high-pitched ranges normally used by creatures such as bats and whales.

To that sea song, Mordecai added magic. The small creatures were going to be effectively bards, their songs enchanted to bolster and heal their allies, or to enthrall or instill dread into their foes.

He also gave them a small complement of normal enhancement and infliction spells, such as those used to quicken or strengthen allies or to slow or weaken enemies.

They were simple. His next project was a little more complicated.

No one had been able to bring a live specimen of a creature closely related to jellyfish from the ocean to their territory, so Mordecai did his best to evolve a close match from their existent slime creatures. The result was fairly close, so he was satisfied with calling them crystalline jellyfish

Their life cycle on the other hand, well, he was having some fun there.

At only a few pounds, they would be starting as the smallest of their new inhabitants. They were also smaller than a normal jellyfish would be for that weight, as they retained some of the living crystal properties of their slime ancestors along with a small crystal core to be a brain.

These tiny creatures could be almost invisible when they were drifting slowly, but their thin tendrils were already packed with a potent paralytic. If they were spotted early they could easily be killed before they were close enough to be dangerous, but if a group was distracted by a fight already when a few of these drifted out from behind a piece of coral, it would be fairly easy for them to slip in unnoticed.

They would be growing larger of course, and eventually reproduce when they reached twenty pounds. That was where Mordecai laid an eventual surprise. When they started producing young, the individual polyps would be mostly dormant and act as part of their parent's body. It would be nearly impossible to tell where one ended and the next began, with many of the larger jellyfish's tendrils actually belonging to its offspring.

All of this would change when the crystalline jellyfish received enough damage to make it 'shatter'. This would cause it to split into the parent and the swarm of tiny jellyfish, along with a cloud of connective tissue and gel. The parent would still be about half the size of the combined form and thus a significant individual threat, but its tiny children would be just waking up and running about in confusion as they learned to coordinate themselves.

While individually they wouldn't be much of a threat, the pure chaos of those first several seconds after the split would make it very easy for them to accidentally run into people and hit them with flailing, stinging tendrils.

This would leave the parent at about ten pounds again. The next time it was ready to reproduce, the total weight would be forty pounds with the parent making up twenty of those pounds. The offspring would be the same size, and thus twice as many would be born when the larger form shattered.

Mordecai did not put a cap on this doubling pattern, he didn't need to. Growth would be limited by what they could eat and the time they spent alive.

That was a rule he implemented for all of these inhabitants who were intended to grow bigger. They only aged during the time they were alive, so an inhabitant who died in battle during the morning would lose more than twelve hours of aging/growth for that day.

Individually, many of the new inhabitants would underperform compared to even the river level for a while. However, the environment made for unique opportunities for swarming and ambushing delvers and they had a selection of heavy hitters to back the swarms up.

With that, Mordecai was done with the inhabitants for the ocean zone. Next up was going to be the bosses.