The origins of the Vampire and Lycan races start approximately 1500 years before the films are set. The origin is initially described in the film as a legend but later shown to be correct, Alexander Corvinus a Hungarian warlord who lived in the early fifth century ascended to power just in time to watch his village ravaged by an unknown plague with Alexander the only survivor. His body had adapted to the virus, and through some unknown means consequently making him the first immortal. Later the term Corvinus Strain is coined by a Lycan scientist, Singe to describe the genetic anomaly which allowed this. The nature of the particular virus that affected Alexander is unknown, nor is it known whether his body would've also adapted were it another virus that he was infected with.
Corvinus strain
The Corvinus Strain is a recessive genetic anomaly that uniquely has the ability to sustain and harbor both viruses carried by Vampires and Lycans. This anomaly is the only known gene that is capable of combining properties from both the Vampire and Lycan Strain that would, otherwise, destroy themselves on contact due to the incompatible components contained at their cellular level. This recessive strain is activated once it mutates with the genes of one or more other species. The only known post-mutation examples of the Corvinus Strain are the Vampire and Lycan Strains.
When inherited in its active form, the Corvinus Strain gives its host immortality and superhuman strength, while, additionally, possessing the capability for another stage of mutation when subjected to gene-fusion. However, when inherited in its dormant form, it gives no interaction with the host, whatsoever; thus, giving no indication of its presence from third-party perspective. Still, there remains the capability for the dormant strain to undergo another stage of mutation, but this could only be accomplished if the strain is drawn to its active form by an independent source. One such source is the Corvinus Strain in post-mutation form, that is to say, either the Vampire or Lycan Strain because of their dominance. A fusion with either post-mutation strains would produce extremely potent results, as the dormant Corvinus Strain would be in its consanguineous form. Alternatively, a fusion with both post-mutation strains would produce even greater results, which would be regarded as a Hybrid.
Spread
Years later, with his wife Helena, he fathered three children, two of whom inherited the Corvinus Strain in active form and so his immortality, his twin sons Marcus and William. Marcus was bitten by a bat and became the first vampire. William was bitten by a wolf and became the first Lycan. William became a savage anthropomorphic wolf-beast, something Alexander attributed to his uncontrollable rage.
William went on an uncontrollable rampage, infecting whomever he bit or clawed. Even those killed by William soon came back to life as the effects of William's mutated Corvinus strain proved powerful enough to reanimate the dead, turning them into the first generation of Lycans. Those infected became raging monsters causing legions of uncontrollable Lycan monsters to be spawned across Hungary. To bring his brother under control, Marcus approached the dying warlord Viktor, promising him immortality as a Vampire in return for his army and military expertise in capturing William. His army was also turned, creating the Death Dealers. After many battles against William and his raging progeny, he was finally captured. Viktor betrayed Marcus and ordered that William be locked away for all time in a special cage, the location of which was kept from Marcus. The strain was also carried by the other descendants of Corvinus in its dormant form. The first person who inherited the Corvinus Strain in dormant form was Alexander's third and unnamed son. Through him, the Corvinus Strain was preserved in its pure form, and was eventually passed down to a man named Michael Corvin. Because of the simple ability of the Corvinus Strain to multiply from parent to offspring, anyone who is biologically related to Corvinus' third son is a possible carrier of the strain.
The Vampire, Selene, absorbed the Corvinus Strain through direct ingestion of Alexander's blood, reinforcing the residual Corvinus Strain in her Vampire Strain, and, thus, fusing the full strengths of both strains for the first time. Her strength and healing abilities were enhanced to a level equivalent to that of a Vampire-dominant Hybrid, even being able to withstand direct exposure to sunlight.
The Feud
After William's immediate threat was finally ended, Lycans still existed. Their progeny later proved to be more usable to the vampires and were literally branded as subservient "watchdogs" for vampires during the daylight hours when the vampires' bodies were vulnerable to attack. By this point Lycans had learned enough control that they were primarily human, only changing into their wolf forms at the full moon. A lycan slave named Lucian eventually led a rebellion against the vampires in response to the murder of his wife Sonja, the daughter of the vampire Elder Viktor. She was killed because she was pregnant, and a lycan/vampire hybrid that she would've given birth to was seen as an "abomination." This started a furious war, as Lucian gathered to him an army of Lycans discontented with their service to the Vampires. The war lasted for centuries, with some Lycans even learning how to control their transformations and change to wolf form at any time.
Eventually, around 600 years before the films, Lucian's fortress was attacked by the Death Dealers. Lucian's forces slaughtered them, but Lucian offered the only survivor, Kraven, a deal. He would fake his own death, allowing Kraven to gain advancement, in return for giving Lucian a free hand. For the next 600 years, the Vampires hunted down many of the Lycans, driving them nearly to extinction. However, Lucian was still alive, and forged ahead with a plan to use the blood of a human descendant of Corvinus to turn himself into a hybrid, just as his murdered child would have been.
The films commence shortly before his plan is foiled by the Death Dealer Selene, who alerted Viktor to Kraven's treachery. As Lucian prepared to use Michael's blood to transform himself, he was betrayed and shot in the back by Kraven. As a massive battle erupted between the Lycans and Death Dealers, Lucian barely survived, and when he witnessed the love between Selene and Michael, told Selene to bite Michael, creating a Hybrid regardless. He was killed soon after by Kraven.
Soon after William was freed by his brother Marcus (himself now a Hybrid), as the two brothers united. William soon attacked Selene (who had come to stop him), turning most of her squad into first generation Lycans. She was saved by Michael. William then battled his distant relative, but was unable to kill the powerful Hybrid. Michael ripped William's head off, ending the threat of the oldest and most powerful Lycan.
