The story was located in a stereotypical fantasy world until now. The heroes had to save their land from an evil warlord/sorcerer that got his hands on a magical artifact that granted him the ability to make short trips through time at high cost. He mostly used it to let his ancestors' armies join his war campaign in the present, and to damage the defending forces in the past when they least expected.
In the end the heroes manage to scatter his armies and defeat him. They promised to a guild of elven mages to give them the magical time machine so they would keep it safe.
After the heroes (now kings) die of old age the mages start to tinker with the artifacts, grow possessive of its power and start to clash with each other. They damage the artifact in a fight, and it in turn provokes a time-space anomaly that changes the whole multiverse. Each universe got randomly merged in couples. The important change is that the initial fantasy universe was merged with our real universe in a weird mishmash. The planet of the fantasy world have been mixed randomly with Earth and other planets from our universe.
So now there's this planet (temporary name "Stitch") that is in general respects similar to earth but its continents are:
- The land where the heroes lived
- now attached to it there's 1000BC Scotland
- there's another fantasy themed land attached to it
- then there's a chunk of 500BC belgium and germany
- a bit down there's a valley that comes from an alien planet (and has alien flora and fauna)
- and so on
The new story starts a couple of decades after these events, so most of the civilized creatures that faced this situation have either brutally perished, like one of the fantasy regions, or adapted and flourished, like the Scottish humans. The humans of the world have stabilized and adapted their lives to the new reality. This new world now has old and new castles, roads, merchant routes and so on.
My question is this: I wanted to drop into this stitched together world Halifax, the Canadian city, from 1800 industrial era. BUT, I still want the world to retain his medieval-fantasy style. I want to make it so that the city is all but ruins now, totally unable to react to the almost cataclysmic change, and its remains are dangerously infested but filled with precious "future" technologies. One important plot item will be a newfound project for a game-changing technology, non other than a steam engine.
But I can't think of a good reason why medieval Scottish clans and Celtic tribes should have no problem survive a world-wide mind-boggling cataclysm while a technologically advanced and prosperous city should totally fall apart. Why would tribes and clans from ancient Europe survive this cataclysm, but the industrial city of Halifax would not?