After a matter of weeks, the global population of Zubat had swelled to critical levels. With hundreds of thousands of newly minted Trainers roaming through neighbourhoods each day, catching Zubat and almost immediately releasing them into the wild, entire cities had become no-fly zones.
Nobody was quite able to explain how the population grew so, though. Some odd mechanism of the catch-and-release method seemed to produce more Zubat than there were originally, despite the lack of any intentional breeding or significant egg-hatching. The company behind the revolutionary "Everyone Can Be A Trainer" campaign, Niantic, had remained silent on the issue.
It so happened that one fateful day, a particularly heavy swarm of Zubat had rendered Edmonton, Canada, perpetually cast under a fluttering shadow. Glittering penthouses were reduced to inside-out caverns, their exteriors adorned with multiple layers of blue and purple eyeless bats. Pedestrians scurried about with hands over their ears to avoid being struck by stray Supersonics.
On this particular day, a heavy and hot wind bore down on Edmonton. Combined with some sudden cold gusts from the mountains, and a particularly inclement upper atmosphere, the clouds above the city were turned into a dark mass. Out of this mass was born an invisible dagger of wind that spiralled downward.
The Zubat were caught in its powerful current and swept around and down toward the ground. As the people of Edmonton looked upon in horror, the vast screeching swarm was remoulded into a dark tornado of bewildered wings and teeth.
As the people ran for cover, the midnight twister whirled and scraped its way down Jasper Avenue. Gluts of Zubat were flung up and down streets as they happened to escape the air currents, and for some minutes the only sounds of the city were screams and leathery slaps against windshields. Once the twister emerged into the open space of Churchill Square, its full fury was unleashed upon City Hall. Some witnesses swear that Scott McKeen stood atop the bell tower and joined his brethren as he transformed into a Golbat.
Its energy spent, the tornado dissipated and the millions of Zubat were freed once again to terrorize PokeStops everywhere.