That is Schwanhild Corvix, princess to a forgotten kingdom, supreme monster hunter, and the first vampire.
Millenia ago, a queen bore a child; She and her husband were overjoyed. She was given the name "Schwanhild" for her breathtaking beauty and her ardent ferocity. (In truth, she possessed neither of those traits; You can get anyone to say anything if you're the ruling class.)
In time, the king and queen's health began to decline. Schwanhild's father took ill, and in due time, passed away. For a time, the Queen ruled solemnly on her own. However, when searching for a particular record in the royal library, she stumbled upon a black-bound book. It clearly hadn't been disturbed in years, yet not a single speck of dust lay upon it.
What she found in that book led her to withdraw from regal affairs. The lesser noblemen took over. This absence led numerous power struggles, none of which had any effect of import.
The queen had never been a fool, and that tome contained tools that even an imbecile could use to attain great power. She thought of her late husband and her own declining health. It would be selfish to take that power for herself, but Schwanhild...
The kingdom vanished in a single summer night. Miles away from the castle, some bystanders claimed the entire country was claimed in a bottomless red tide. When morning came, the princess was the only one left.
The buildings: The castle, the stone walls, the peasants' huts - none of them were touched. There was bread and cheese in barrels, wine and water in bottles, but not a single living creature for miles.
For Schwanhild, the consequences of that ritual became evident the moment she built the courage to steal from the long gone subjects. The bread would not satisfy. The wine would not quench. Weeks or maybe months later, she collapsed on the once-border of her kingdom. She was found by a huntsman and taken in.
She woke, with the kindly man's face a foot or so above her own. She was tired, but happy to see him. Perhaps unsurprisingly, he didn't believe she was a princess. Bothered, she sat up, bringing her roughly level with his neck.
The huntsman's dog let out a racuous cry as Schwanhild, not even aware of what she was doing, leapt upon the man. By the time he reacted, it was too late. She'd pierced his veins, drawing thick streams of blood into her mouth. The hound ran. Schwanhild, hunger sated for the first time in months, sat up.
She ran.
The sun, which had always been a sign of joy and strength, scorned her skin. By the time night came, she was covered in horrifying blisters, which couldn't decide whether they wanted to drip blood or fall off entirely.
She'd been fleeing for hours, and her legs burned sore, but she did not feel the slightest bit tired.
The ex-princess took a look at herself. She'd made a mess; Blood stained the entire front of her white dress. It had been a gift from the Duke of Somewhere. He'd always been kind, and she'd always looked forward to seeing him for royal affairs. His son was shy, but he'd been one of her closest friends.
It was gone. The white dress and the kingdom she'd once called home. She was starving.
The next attack was more planned. She wouldn't kill them, just restrain them and take a little blood. There were lots of people, and she only needed a little bit. Just a little bit.
That would be the decision she would come to remember as the greatest mistake in her life.
Schwanhild moved on long before the changes set in. Long before her victim found that bread and wine would not fill. Long before they began to attack others.
The huntsman never had to suffer undeath. The same could not be said of the other men and women she took blood from. The ones she left alive.
By the time she found out, it was too late. One of her children gained repute - a nobleman: Lord Tepes, Vlad the Impaler, or, most commonly, Count Dracula.
She ran.
She ran until she could no longer see that cursed fortress on the horizon.
She ran until her body refused to run further.
She looked into her reflection in a lake, and she couldn't see herself. She saw the huntsman. She saw the thousands of lives she ruined.
If this was the price of her life, she did not deserve to live.
She pulled out a knife, but the blade would not spill her blood. She threw herself into the waters, but she did not drown.
Her stomach convulsed in disgust. She felt vomit rise in her throat.
The lake was crimson by the time she finished, but then, when she looked into the surface, it was a woman in a white dress she saw. She was starving, and weak. But the price of her life was not for others to pay.
She ran. She ran until she saw that cursed fortress on the horizon. She wasn't the only person. Six others - a knight, a priestess, a sorceress, an alchemist, an assassin, and a cavalryman, the most talented and skilled masters of their arts - had been gathered to take out the threat looming on the horizon. Under the guise of a monster hunter, she joined them.
When they stormed the castle, brutal though his forces were, they thought they would triumph.

They were wrong.
The king of vampires called out Schwanhild for what she was. For just a second, they turned on her. In just a second, the King of Vampires slew them all.
For the first time since she woke up in her kingdom alone, Princess Corvix cried. Bitter, painful tears hit the ground. This mistake was not one that could be fixed, especially not by her, the monster mother of monsters.
Not alone. Words that echo to her even today resounded through Dracula's throneroom.

"Why do you cry, Schwanhild? Monsters do not cry for others."
These six... They could not be called friends, but they had a common goal. She pierced her veins. Streams of blood from six men and women were drawn into her mouth.

She was not a monster. Monsters do not cry for others.

Her hunger didn't just fade. She felt full. Almost too full. Six others, the most talented and skilled masters, gave her their strength. That was the last blood she would ever drink.

Count Dracula's millions of stolen souls couldn't hold a candle to Schwanhild's willingly given six. In just a second, the princess of a forgotten kingdom, supreme vampire hunter, and the first vampire slew Vlad the Impaler.
The seven souls escaped that castle. When they woke, they were near a lake. The reflection did not show Schwanhild. It did not show  a knight, a priestess, a sorceress, an alchemist, an assassin, nor a cavalryman. It showed someone else entirely. It showed Scironex.