So this post mostly covers the adorable, apparently stinky birds featured prominently in every Final Fantasy game, but that little bit at the top about "mimic-germinites" opens up a bit of worldbuilding for Final Fantasy XII that is absolutely bonkers and I love it to pieces.
In FFXII, a lot is said about the ancient past, about the Dynast-King who united the lands and how that definitely didn't have any sort of geopolitical or religious consequences at all, don't worry about it, it's not portentous or anything. But there's other strange things you'll find every so often. Like, this is a world with airships and magical crystals that power everything.
So why are there vast fields of abandoned oil derricks and storage tanks?
This is never really expanded upon in the dialog. One of the great empires drilled for oil here, and were chased away by the indigenous people who live in the Sandsea. No, not in the region, in the sand. Which literally moves and flows like water. It's a literal sand sea. There's fucked up fish in it and everything. Absolutely wild.
The game doesn't really expand on that further, and because you're mostly boggling about the sand, you don't think much further about it. But tucked away in a corner of the extensive and delightful bestiary lore entries, there's this passage:
We all are told at one time or another, but how many of us recall that Ivalice is covered with mimic-germinites? Easy to forget, as they have little impact on living creatures, but any moogle worth his hammer could tell you the horribly corrosive effect the little devils have on the metals most often used for engines and vehicles. All the better for airships, which fly high above the germinite clouds, yet a sorry state of affairs for those who would make their journeys on land. The next time you see a party traveling by chocobo and chocobo-led wagon, you will know why they're the preferred means of overland transport, won't you.
So. The plot never bothers to explain this either, but if you're paying attention to the bestiary as you travel through the Sandsea region, you can find a series of diary entries from a mage who was commissioned centuries ago to create an artificial, living, parthenogenic construct that could be snuck into a dragon's hoard, lay eggs, breed an army without being noticed, and then attack. This concept was a failure, but as a petty revenge against their annoying patron, the mage snuck a mother-mimic into the patron's cellars and left it there.
This seems like it would just be a funny little story, but the setting of FFXII features a very particular system of magic: it's basically radiation. It's mutagenic. While a certain amount of it is normal, or even healthy, too much can do precisely what you think it would, because this is fantasy fiction. It makes giant technicolor mutants.
And also, apparently, tiny mimic sky-plankton. That eat engine blocks and electrical cables.
This, quietly, and completely unexplored by the game, implies an absolute apocalyptic level of technological collapse. A civilization that mixed magic and easier, more powerful electrical technology, completely lost its long-range ground transport and untold amounts of societally critical electronic systems. People had magic to fall back on, but it wouldn't have been painless. They had to completely retool how people and supplies moved across the world, how countries held themselves together, how food and medicine were produced, how they kept their homes lit, how they cooked, just about every single aspect of life was affected. This world had cars, and then artificial bugs ate them.
That is WILD. And it entirely exists in backstory, never directly addressed. It's just there in case somebody says "why do some characters have smooth-bore pistols but there's Star Wars-y airship dogfights?! This tech makes no sense!" It's because if you brought one of those airship-mounted machine guns down to ground level, the bugs would eat them. Checkmate, nerds!