[ Magic injections-- water is saturated with magic, perhaps to resist the long-term negative effects of the magic at this depth injections of similar properties, designed to gradually increase resistance? A vaccine, in a way-- failed, poison, their bodies are not meant to take that level of magical toxicity, even native as they are. Children and elderly likely even more susceptible to illness and eventual death, cure unlikely. If those monster guards and the people in the videos were any indication, physical mutation from overexposure likely if the user survives... although... their bodies seemed to form the meshed in wings and tails rather well. Were those natural? Testing, regardless, to this extent and on children-- disgusting.

She checks to see if she still has the extra tapes in her shirt, before walking. ]

...Technology at this level likely is being able to hibernate, without anyone to show it to. It does sound very similar.