There had been many researchers at the Southern Marine Research Laboratory, but the office of only one interested Us.

Oscanion had been the only mage employee here. As a black mage, he would have participated in suppression of more unruly specimens. He was known to have been subjected to the monster's most powerful spell. Had he known anything? If he did, it would likely be in his old office.

We searched the office space for some time, before finding the door labeled "Oscanion Paliter, Senior Researcher."

Even after 964 years, the enchanted lock held, until Izena channeled some acid onto it.

"A black mage never needs a key," She joked, and We chuckled.

As We entered, the first thing We saw, on Oscanion's desk in the right rear corner of the room, was an image of him and many other staff, smiling while holding a storm nymph about to be released back to the ocean.

"You can't be serious..." I whispered.

"Is that, the father?" Izena wondered.

"There's no way it's not." I was filled with rage. To turn a man who smiled like that while holding a rehabilitated storm nymph, whose generosity had inspired nostalgia that brought that nymph back after becoming a storm fly and father a millennium later...

"Unforgivable," Izena whispered.

There was a single sheet of paper on Oscanion's desk, faded and decrepit but still recognizable as handwritten notes in 'Middle' Ezentic, held in place by a paperweight. I used white magic to repair the sheet back to legibility.

We began to read.

"The vast majority of ocean life uses either black magic for its general combat utility, or green magic to leverage its environmental advantage. White magic is sometimes seen in more passive, defensive organisms, and blue magic is rare, but has been observed in organisms that use it to manufacture robust shells and similar accessory items. Recently, we have discovered at the ocean floor a creature that uses red magic, the first documented case."

We took in a sharp breath simultaneously.

"We do not know how it entered the facility. It may have a microscopic larval stage. Regardless, it cannot be allowed to remain inside. I plan to attempt to euthanize it as soon as possible, as its power grows constantly, and have prepared this description of the problem in case I do not succeed."

The poor man. It was obvious that he had not succeeded. We would need to clear his name.

"It lives inside the ice at the ocean floor. We did not think such a thing possible, due to the extraordinary pressures, but it has an extremely sturdy enchanted shell. It never leaves the ice and never exposes itself outside the shell. I suspect that it lives in a symbiotic relationship with a blue magic casting organism, although I doubt the shell-provider is a willing participant, for reasons that will soon become clear."

We agreed: consent is optional in this thing's worldview.

"Direct attacks against it are unlikely to be able to penetrate the ice and shell unless they are extraordinarily powerful, beyond human limitations."

"Good thing We brought a Black Goddess," I said, and Izena snorted.

"I hypothesize that its pre-magical ancestors were scavengers, eating the corpses of monsters that died and sank to the bottom. Eventually, the species evolved the ability to coerce prey to swim down using red magic, until they were killed by the pressure and became the corpses it could feed on. A passive scavenger turned into an active predator that uses mind control as its hunting strategy."

How insidious.

"Due to the typical inconsistency of its food supply, it can probably survive for a very long period without eating. However, it shows a strong instinct to feed voraciously whenever it has the opportunity, killing as much as it can whenever it can without limit, as it is doing now in this facility."

Without limit indeed. It had tried to eat the entire surface population, and still not been satisfied!

"It does show an understanding that it can be a net gain in the long term not to consume mind-dominated victims that are useful in some way, probably due to its relationship with its shell-producing symbiont. It has been observed to program its mind-slaves to collect and deliver food to it, and to keep particularly powerful slaves as guards and for reconnaissance."

We shuddered. Eventually, it had grown powerful enough to enslave a large fraction of the human population, and use them to "collect and deliver food to it." I guess Oscanion himself counted as a "particularly powerful slave."

"The organism feeds by sending nanoscale tubes through the ice, drinking the nutrients as the corpse rots, while minimally exposing itself. Its desire for rotting corpses is so strong that it is imprinted on its mana, giving it a foul stench and sense of decay."

I had suspected that this was what caused the rot aspect. It was, in fact, foul, as both Izena and I could testify.

"Upon identifying it, we initially applied our normal policy of non-intervention in nature, and allowed it to continue its routine, but recently it has become clear that its power is far greater inside the facility than it could possibly be outside of it, given that it does not appear to be a major player in the oceanic food chain, and I think I understand why. The facility is one large enchanted cylinder built to endure the water pressure, but also to be insulated against magic in order to protect against the spells of the specimens in the facility. This also works to contain the red magic of the organism inside the cylinder, so that instead of spreading spherically and thereby dispersing at range, it remains collated up to the surface. The net effect is a dramatic increase to the upper limit of its hunting range, lifting its range out of the scarcely-populated deep abyss, to the more densely occupied upper layers."

"Look, cylinders are bad," I said. "Domes are much better. The Rokeshans really do have good taste."

Izena completely ignored Me.

"That's why We were attacked as soon as We entered the cylinder," She said. "The building acts as a massive amplifier. It may have been trying to surprise Us with the strongest attack it could manage, and the Guards' amulets better suppress it outside. And that amplification is also why this particular one became so powerful despite no one ever having heard of this species before."

The next passage confirmed Izena's second idea.

"This increased range is ecologically disastrous, allowing the organism to access vastly more prey. It has rapidly become more powerful as a result, creating a positive feedback loop. When we first realized this, we attempted to remove it from the facility by filling the lower chamber with fully deuterated water, hoping that the change in buoyancy properties would either float it out of the ice floor so that we could capture it, or annoy it by making it harder for it to feed on lower density fluids from decaying corpses, so that it would leave on its own. But, it remains locked inside the ice unperturbed, and now I intend to abandon our nonlethal principles and pursue lethal means, starting with adding acid to its enclosure. I feel that I must act quickly, because every moment of delay allows it to grow more powerful as its range creeps upward and it acquires more and more mana from its prey."

Even if he managed to try that, We knew it obviously hadn't worked.

"Unfortunately, that requires me to go down to the floor level, where its powers are strongest. I hope to be able to act quickly enough that it will not have time to establish control."

He could have fled. He had tried to be a helper.

"We will succeed where you failed," We said. "And We will use very lethal means indeed."

As We walked outside the office and descended into the aquarium level, We saw that the enchanted feeding system had long since run out of mana. That was mostly encouraging, in My opinion. Anything in here would have been starving for a long time, not as powerful as it might have been.

There was no evidence so far that anything else in the facility was still alive. Our enemy had likely eaten well, a millennium ago.