Oddly enough, in a way the present day seems the most like Ildios to me.
Not exactly like it, of course. We were more advanced than the way the world is right now through our more extensive use of magic. But in our day there were of course remnants of the Aughylian Empire around that nobody could use, ancient mystical technology that was simply collected and traded among the rich because it couldn't be activated. Whereas here it's everywhere, littered among ruined cities and thrown in gorges and rivers just to get it out of the way, but still otherwise just as mystical. And just as unusable.
Society regressed once more. The wars of supplies led to much of the world's knowledge being destroyed in the crossfire, and as waves of people died out everything fell back to simple farming once more. So much lost, it hurts them to hear of it, as the eldest of the people alive tell stories to their youngest descendants, told to them by their eldest forefathers while they were at their youngest, of the way it was during the end days while the supplies were dwindling but the technology was still in use.
I think what hurts this people more than anything else is that they can still see it all. They can see the road vehicles lying on the ruined streets, they can see the air vehicles lying in the fields where they fell from the sky and were too heavy to move. Scavengers search ruins of the cities for scrap metals and wood and tools that can be put to use in some way, and they all see all the wonderful conveniences of the past that can no longer be used anymore. For most of them, they don't even know how many of these things were even used, and their guesses can get interestingly wild. It hurts them that they know, they can see for themselves that the world used to be a better place, and there's nothing they can do about it.
They live now in a simulacrum of what was lost, scrambling to be like how its told in the stories. Approximations of technologies of the past are used as best as they can. Animal drawn carts, both on free wheels and drawn along set path rails. Flame based lighting, either from candles or piped in gas where available. Where available, food is kept cool in boxes filled with ice, or in places where ice is not available in containers taking advantage of the evaporative cooling properties of water. To the people, though, it's seen as just an approximation, a reach toward the past that has been lost to them. Most don't realize that either they have either invented new technology to do the tasks without magic, or reinvented technology that already existed in the past that was then modified to work with magic when the crystals were created. They could certainly do worse, as far as levels of technology are concerned. If only they would realize that they are looking toward the future, and not looking back to the past.
Interestingly enough, the biggest advance has actually been the Evreux. With devastations to their underground systems, they had to go through and rebuild much of their infrastructure, giving them opportunity to overhaul and expand it. Using some of the technology we saved, combined with other technology they retained from the height of their civilization, they've created more advanced trains and other vehicles, increasing in speed and allowing for much faster travel between their settlements, as well as adding additional redundancy and alternate paths just in case something like before happens again. All of it based on more advanced technology and materials that require much less maintenance than before, allowing much easier use of the vast underground network.
Along with expansion of their networks, they've also expanded their own underground towns and cities. With their belief that leaving the planet will lead them to disaster once again, they've adopted the idea since the time I first met them that expanding further into the underground will bring them more in tune with nature and the planet. They've developed new technologies to allow them to more easily grow food underground, which has allowed them to expand their population, and with it required them to build larger and more complex underground cities. Now complexes around key rail stations have expanded that can hold up to a thousand in them, or more as they expand further. Although, to their credit, they're not abandoning the surface, and have a policy of compulsory service among their people of living topside to grow and hunt for a time period so they better understand where they came from and where they are going.
They've also taken the more advanced medical techniques and continued pushing them forward, again combined with their technology of the past. Implants and limb replacements have gone from clearly mechanical to indistinguishable from regular flesh, and requiring much less maintenance. Enhancements to supplement what has been lost by age are commonplace now. Age hasn't been kind to me myself, but thanks to several surgeries by highly skilled experts I've had knees and hips replaced, and enhancements to my musculature and nervous system to allow me the freedom of movement that I once had when I was much younger. I still look like an old woman, but in combat I would no longer move like one, something which would be sure to confuse anyone wishing to stand against me.
As they've been expanding their technology, being the only human living among them has been... a little difficult. Their size compared to mine means some things are not well built for someone of my height, making things a little cramped for travel. Such as their rail cars, I have to more often sit on the ground to keep from bumping my head in the small trains traveling from city to the next. It's a good thing the trains are much faster than they used to be.