As the Hylden's Blood Curse rendered the Ancient vampires sterile, they eventually found a way to continue their bloodline by transforming humans into vampires themselves. The first to be turned was Vorador, at the hands of Janos Audron (as his reward for forging the Reaver). Many of the initial human Guardians of the Pillars were abducted by the remaining Ancients and turned into vampires when they came of age, which ultimately led to Mortanius and Moebius rebelling, successfully overthrowing the Ancients and taking the Pillars for humanity.
The new vampires flourished and began to turn others, eventually growing so numerous that the Sarafan led a Guardian-sponsored Vampire purge during the Nosgoth's early history, eventually succeeding in slaying Janos himself. Ironically, this act would spell the Sarafan's undoing and ultimate demise; Vorador, enraged at the slaughter of his people and the demise of his sire, invaded the Sarafan Stronghold and brutally murdered six of the Guardians in retribution for their support of the Sarafan crusades, while the time traveling wraith Raziel personally slew the six Sarafan commanders who carried out Janos's murder.
The vampires of this world subsequently continued to thrive until the events of Blood Omen, when the newly turned vampire Kain used a Time Streaming Device to travel back in time and assassinate William the Just before he would become the tyrannical warlord known as the Nemesis, bringing about the second timeline; however, Moebius had planned for this, and used William's murder at Kain's hands to gather a citizen army and bring about a second Vampire Purge, eventually reducing the vampire race to only Vorador.
By the time Kain returned to the present and realized the full magnitude of his meddling with history, Vorador was captured and guillotined before a bloodthirsty mob, leaving Kain the sole remaining Nosgothic vampire.
Vampires (second generation)
Vampires (era following Blood Omen)