The world was normal for the most part. Physics was a thing, time still flowed, the moon rose and fell. People were born, aged and died. Nothing too spectacular.
For a while.
Then the dragons came.
To the general public it was a surprise. One day life was as it should be, people woke up, drove to work and did mind numbing tasks to pay the bills. Crime happened, politicians profited off the masses, and assholes made life difficult. Normal every day stuff.
Then things started happening. GPS stopped working. Mobile devices started losing signal. Power plants started shutting off. Any generator larger that a small car started going on the fritz. People panicked, and mobs of people who are confused and unhappy will do what mobs have always done.
It was worse for the governments. There was no warning. There was no sign of what was to come. No strange earthquakes, weird signals, strange energy readings. Nothing. And really, how could they have known. Magic was something they could never have planned for.
Because magic broke all the rules. How can a device made to read the inputs of logical, measurable, natural phenomenon that follows the laws of physics detect that which is there and yet isn't. You can't detect magic anymore than you can detect souls, fate, or the presence of gods.
And dragons are creatures of magic in physical form. God's are beings of magic that exist outside the physical realm, so therefore can choose not to effect it. Dragons do not have that luxury. Nor would they care to hold back their awesome might and presence.
So when 21 dragons descended upon the earth, their very beings affected the physical world like a magnetic pull that defied all logic. They where like a combination of a walking EMP and radioactive emitter. Anything more complicated than a telegram refused to function within a mile of a dragon. The effect was exponential when there was more than one dragon in an area. And 21 dragons broke the modern world.
In the following years there were many attempts to learn where the dragons came from and why they came when they did, but all were left with speculations and non-answers. Dragons did not seem to care for the curiosities of mortals. They barely kept from wiping them out like pests. When military organizations inevitably tried to shoot them with whatever weapons still worked in the presence of these awesome creatures, they were summarily ignored or mocked. It was later revealed that dragons were outright forbidden from extermination humanity by the Gods, on account of the dragons intruding on their domains and the homes of humans to begin with.
The only real explanation humans got for that was something to do with ancient laws and rules of hospitality. And so humans survived the coming of the Dragons. But like all of reality that is influenced by the presence of dragons, humanity was changed.
It was a chaotic thing. People suddenly sprouting wings or randomly throwing fireballs. Mutations and arcane phenomenon became a common occurrence, and not all of them survivable. Horror stories of butcher science and torture labs became a terrible reality. With the central government in shambles and regressing to technology that was outdated in the 1940's to communicate, nobody was capable of completely stopping these horrors.
Thankfully the Gods stepped in. Younger Gods that never made their presence known to a humanity that no longer needed them. Gods of wisdom and knowledge where where taught by elder Gods such as Athena, Saraswati, and Thoth. Gods of justice, Gods of fate and magic.
And thus, the System was born. A new God. The first to be born outside of the established pantheons in millennia. The System was not what could be considered normal for a God, on account that it's being was partially form in an artificial manner. It's temperament could be best compared to an advanced artificial intelligence, being logical to a fault and being confused by social cues. But as a legitimate God it was far more capable of adapting to its own existence and situation.
And so humanity gained a powerful tool to help translate and rationalize this new reality of magic and wonders. A System to help quantity and direct the chaotic mess that wild magic was doing to humanity, turning a wild and forced evolution into a more streamlined and survivable process. Mutations turned into blood gifts and subspecies, random powers shifted into schools of magic, and a host of other changes.
Possibly the most important thing the System ever did was create the dungeon towers. With the Systems help humanity could survive brushes with wild magic, but humanity wasn't brushing up against a small source of it. They where drowning in a veritable ocean of the most potent source of wild magic in existence. So the dungeon towers were built and designed as a magic heat sink. The towers would draw in all the wild magic it could into itself and leave the ambient magic levels at a much more safe level for humans to survive.
But that left huge banks of power with nowhere to go. Some humans learned to tap into that power to fuel massive enchantments that allowed for huge cities to be built around them, while most were used as ways for humans to safely absorb more wild magic. With the Systems help, absorbing wild magic led people to grow stronger in both power and vitality. These gains were displayed by the System as 'levels'.
The constant accumulation and processing of magic power into a more pure and stable form of magic brought the earth's ecosystem into a more harmonious balance. As long as the dragons didn't do anything to reality breaking at least.
Thankfully the dragons seemed content with their new resting places and rarely moved more than a few miles from their homes. Some even traded using their magic dense scales as payment for food and luxury items. There was even one dragon in what was known as the Asian continent who liked to shape-shift into a human form and explore human settlements.
And so over the course of 80 years the world of Terra was changed forever.