There was a time, thousands of years in the past, when the Earth orbited the Moon. The hours of darkness predominated the timeframe that we call night and day. With the climate and temperatures being several degrees cooler than they are now, it was no surprise that the race known as Vampires rose to become the dominant species on the planet.
There were two primary casts of Vampire; The Alphas and The Betas.
Alphas were high-ranking individuals who achieved their status through aggressive determination, physical strength and the building of alliances within their own Clan and when the need arose (political or otherwise) other Clans. Only Alphas were accorded the right to reproduce.
Betas served as administrators, dealing with the day-to-day matters. If they proved their loyalty, they could, on occasion, act as second-in-command to the reigning alpha.
At the time the Vampires regarded the race known as Homo sapiens as merely a ready food source. But as this lesser race gradually developed, they saw a potential new use for them, as slaves. The males they used to perform the menial, difficult and dangerous jobs. The females were ideal as concubines, as female Vampires only became fertile, and therefore sexually active twice a year, Vampire Alphas now had the perfect solution for their sexual frustrations.
But nothing ever stays the same.
Change was inevitable.
Over time gravitational shifts pushed the planet into its current orbit. With the Earth now orbiting the Sun, daylight predominated with temperatures increasing, Vampires were forced to find refuge out of its fiery glare.
By contrast the Human population greeted the environmental changes with enthusiasm, greedily relishing the Sun's warming rays.
Not to be outdone, evolution ensured several dramatic changes of its own that saw the once lowly Homo sapiens grow and evolve. With enhanced intellect they established their own cast system and refused to be viewed as lesser beings.
Evolution inflicted a terrible blow to the Vampire population. Birth rates dropped dramatically, ensuring that they could only produce offspring every ten years, then every twenty-five, and finally every one hundred years.
In less than millennia, Humans outnumbered Vampires one hundred to one, with the trend continuing into the foreseeable future.
The Humans saw their opportunity to become the dominant species on the planet.
The Vampire's were outnumbered and overwhelmed. Eventually banished permanently underground, never to be seen again. With all records of their existence destroyed, they became nothing more than folklore and fairytale.