Eberron: Eternal Chaos
A variation on
Wayfinder's Guide to Eberron based around the idea of magic being more akin to a raw chaotic power source. The technology of the world is powered by this raw energy, but attempting to manipulate the energies directly is a recipe for disaster.
The custom rules (5e variant) encourage the widespread use of magical items and character customization. Magitech is widespread throughout the world, and is largely based on discoveries from the ancient Hath ruins scattered throughout and underneath Eberron.
This is how we find the world, but it's not how it has always been. What happened to make magic this way? Is magic this warped throughout the universe? Why did the Hath suddenly disappear so many Millennia ago? What dark secrets about the very nature of our reality have we yet to unearth?