As part of the truce agreements following the Crimson Dawn, some technologies and fields of scientific research were restricted if not even banned entirely. As a result the world seems mostly locked in the 1940s in terms of technological advancement, but with some notable exceptions and the addition of magic.
Fully automatic firearms are banned and the only rapid-fire guns accepted are gatling guns or similarly hand-cranked firearms (though some loop-holes in the ban have been abused to mount rapid-firing turrets on vehicles and aircrafts). Following the Spanish Flu, which turned out to be an evil plague summoned by the Mythicals to pave the way for their return, biological warfare is also banned. However, Chemical warfare isn’t: albeit regulated, it is deemed an acceptable response against Magical warfare, which is by nature near-impossible to regulate. Tampering with “Dark magic” (like Necromancy) is generally frowned upon by the public opinion though, so much so that some countries do sanction or even forbid its use in public, and it will definitely draw the attention of the Guardians of Gaea.

Speaking of magic, the way it is understood by most scholars is that, to put it in relatively simple terms for us, it is the “software and programming code on which the universe itself runs”. Under this analogy, the extremely precise gestures, symbols and materials required to cast spells work like “accessing the console” and running “cheat codes”. Anyone could potentially learn and use this code, but in reality few people manage to master the art of spellcasting because much of it still remains to be discovered to this day. The only advantage the Mythicals have is that they were the first to discover the basics and pass them down from generation to generation, to the point where today many of them memorize various sets of spells and magic formulas at a young age, before they even learn what they mean. It would be the equivalent of knowing how to say some words or basic sentences in a foreign language, but being unable to speak or understand that language.

Having established how magic works, it’s easy to imagine how synergetic it can be in tandem with technology: you could modify the properties of a material to meet the desired specs, shape it however you want to build a perfect machine, make engines that run forever without fuel and so on… This niche use of magic is called Technomancy and is as valuable as expensive, so conventional machines are still the norm around the world for the commoners in cars or chainsaws, while the technomancers focus on bigger stuff like ships or electric generators for cities. Furthermore, any technomancer will tell you that not even magical machines are truly perfect: you can enchant an engine to run forever but you can’t eliminate friction (yet), so eventually it will grind itself to pieces… and some even say that magical machines tend to grow an ego if they are never stopped…
And let’s not forget the most notorious device of all: the one that caused the Crimson Dawn. Its makers were so horrified and filled with guilt by their creation, that would later agree to do a “damnatio memoriae”: they destroyed the data and documents regarding their research and even performed a ritualistic suicide with magic, cursing the knowledge itself of the device and its creation. The ritual’s effect is that anyone attempting to re-invent the device or finding any undestroyed data of its original research is struck by amnesia.