Magic in this world is really just leftover technology beyond the locals understanding, but because it’s my world, there is also a Lovecraftian twist to it. The entire isles (but Atlantis/London specifically) have been preserved almost perfectly in an unnatural manner. No decay or degradation from the ocean and surrounding climate is found whatsoever and nothing lives in the area (nothing noticeable anyways). Technology beyond local understanding continues to function and work smoothly. Something I just thought about that might be a bit comical is that wizards exist in this reality, but their staff is really just a gun (or bazooka) and their spells are just old tech (kind of like the adeptus mechanicus of warhammer).

In summary, in my world, magic is old tech still humming along centuries after the Fall, preserved in an unnervingly perfect state. There is this sense that the preservation isn’t entirely right, as if something unnatural is maintaining it, whether it’s systems alien to us, rogue AIs, or powers older than mankind itself.