The Planes of Positive and Negative energy.

Once there was a plane of pure energy known as Anu. The energy of entropy and extropy, life and death, balanced as one in equal measure. The realms were tied together by the union of two beings, King Arbor and Queen Sanguine, who were embodiments of positive and negative energies respectfully. The realm was filled with beings of both kinds, and existed in perfect balance of positive and negative forces. Positive energy represented the beginnings of life, growth, birth, and positive emotion, and Negative energy represented death, decay, Undeath and negative emotion. And so long as you could find positivity or negativity within the realm you could find its inverse to balance it. As was the natural balance of all things, until an event known as the “Age of Aloeradin”, swept across the planes. The king and queen of Anu cared little for the events that rocked the other planes and where perfectly content maintaining amnesty on their own plane, however aloeradin brought a wave of negative energy across the planes that began to unbalance Anu. Aloeradin took note of the influence he was having on the plane of Anu, and Aloeradin saw a potential ally in Sanguine. He began to contact her with speeches of how she could expand Anu infinitely and encompass the entire material plane within its energy. Arbor had no interest in this and simply wished to maintain his plane in peace, but Sanguine was filled with the fascination and avarice of ruling an even larger realm, with no influence from Arbor. Normally these feelings would be easily quelled but in this instance Aloeradins influence was clouding her better judgement. And so she would take of the creatures of her realm, choosing among the most powerful and destructive and she sent forth her army, The first Vampires. Among them were the horrific beasts such as Katakans, Vhargests, Ekimaras, but the most powerful and terrifying were the Elder Blood vampires. They perfectly resembled beautiful humanoids but held within them unmatched power over blood, death and magics combined with supernatural strength. The Vampire armies served under Aloeradin during his reign of terror. The only thing that would quell them would be when an elven queen referred to only as the Raven queen pleaded for help from Arbor, who was distraught by his wifes actions. He released a legion of his own. Warriors of pure positive life known as the Luminare, who were made as exact opposites of the legions of Sanguine. The luminare were instrumental in winning the War of Death and transitioning the mantle of death to the Raven queen.
Once the conflict was punished, Aloeradin had fallen and his 4 horsemen were banished or missing, punishment was placed upon the armies who served him including Sanguine. Moralin, the king of the gods, decreed that Anu would be split into two realms, Anu-ar the realm of positive energy, and Anu-as the plane of negative energy, so sanguine would know what her world of death would have been like and suffer it for eternity, with no ability to leave again. As for the vampires, those who were still loyal to sanguine were given the ultimate punishment, to be trapped on the material plane never to return home to their queen and exist everyday fleeing from the sunlight. Those vampires who did turn to the side of Luminare however, were redeemed of their curse of vampirism, but never again could see their home and must see out their punishment in hopes of seeking out redemption so they may one day see their home reunited as one. As for the Luminare, most would leave the prime material, but some would stay dormant to forever watch over their cousin in case they would attempt such a conflict again.
Over time the Elder vampires would pour all of their rage and hate into a wicked curse to displease Moralin, and created the curse of vampirism which could be bestowed upon any mortal creature, the first of which was a man named Strahd von Savorich. This diluted form of vampirism was far weaker than the elders, but it was still a powerful blood curse. The blood within these vampires would twist their minds to feel almost entirely the emotions of their bloodkin, and to forever have a longing to return to a home they had never been. These Vampires started the religion known as the Sanguine Eternal, who maintained they had never lost the war and were simply only biding their time until one day they could enforce the will of their queen once more.