The Beginning
Though how Yersinia came to be is unknown, the epicenter of the originating plague is thought to be in or around
The Sea of a Thousand Currents, the first strain having presumably been incubated within young Guardians who'd come into contact with the disease when they first began their 'search'. The rest ensued in a bad chain of events with the infected dragons traveling unaware, contaminating other inhabitants who in turn passed it on other beings, so on and so forth. Smaller breeds such as faes and nocturnes who were affected quickly became the first casualties of the mysterious illness, their small bodies unable fend off the disease. Larger dragons such as Imps, Ridgebacks and Guardians were more fortunate, as their bodies were able to combat the disease a bit better than their smaller comrades... if being driven insane by fever could be considered lucky. This caused a drastic change in personality, turning them into the foul creatures they are today.
When the disease first started to spread, many clans were at a loss. The rising death tolls caused widespread panic and led many clan leaders to do drastic things, including finding scapegoats, many being Beastclans, and dragons who were unaffected due to isolation or other factors. Accusations soon began to arise that those in question had caused the disease by deliberately poisoning watering holes and wells. Many other incriminating suspicions followed, as well as suggestions on how to combat the infection. Then an idea was proposed by the Nature flight, which had suffered major casualties: employ dragons of the Fire flight to exterminate potentially infected groups in "controlled burnings" since the immense heat they could produce made it almost impossible for disease to incubate.
The flights agreed.
The Burnings
By the time the flights decided on a course of action, much of the population had been wiped out. The Yersinia became one of the most devastating pandemics in dragon history, with death tolls peaking most severely in the Nature flight at 30–60 percent loss of its population. Overall, the emergence of Yersinia reduced the world population from an estimated 450 million to between 350 and 375 million.
When the burnings began, the plan was to round up "priority number 1" infected, those whose bodies were completely consumed by the disease, with no chance of being healed, and 'Certain Dragons who had become too dangerous and aggressive to keep around the public'. The Burnings were successful for the most part, as much of the infected were wiped out. Towards the end of the 4th year since the emergence of the Yersinia, the disease seemed to have petered out.
That was, until stranger forms started showing up as something known as "Mutant Yersinia". These were presumed to be elder Yersinia, among the first infected, who survived the Burnings and had begun to breed. These Yersinia demonstrated greater strength and immune against any and all attempts to wipe them out. This included a new method of exposing victims to various disease, a resistance to heat, and a resistance to any and all drugs that were used to try and heal them in the beginning.
Their evolution is all thanks to Plaguemama, who'd found them to be most intriguing creatures and refused to see their existence extinguished. Instead, she blessed them with these new traits.
The Plea
Afraid of having to go through another war against these ticking time bombs, many pleaded with the Plague flight, who had been silent throughout the years this was going on, to take the disease-ridden pests away and keep them within their borders. The Plaguelings agreed, believing that the Yersinia would come to be of great use for spreading the rot and disease they loved so much.
And so many of these dragons were banished to the Scarred Wasteland while others who refused to leave were killed by survivors of the pandemic. With their banishment came the end of the Yersinia plague, but marked the start of the Yersinia Clan under the watchful eye of the Mother of Pestilence.
