A/N: I've spent the past, like, year considering backstories that explained Elsa's powers. So this is kind of my explanation, which I've finally gotten around to writing. This is kind of just like a quick overview, I was going to go into detail but didn't know if I'd have to bump the rating up or not. So it's just a one-shot.
It happened approximately five hundred years ago. It was the midst of the Dark Ages. The 1300s. People practicing sorcery and witchcraft thrived, though they were executed if their magic was revealed. It, however, did not stop them, and this is where our story begins, dear reader.
A young girl had been raised by a witch. She'd escaped as soon as she could, swearing she would never practice the same things her mother had. Her mother, however, was incredibly strong in her magic, and was able to find her. Falda Faramund soon found her daughter, tracked her down, and cursed her. Instead of freezing her heart and killing her, she ensured that her firstborn would have magical wintry powers. The child would become an outcast and, if its powers were found, would be slaughtered.
Two years later, the young girl married and subsequently produced her firstborn; a daughter she named Valkyrie. She knew the child didn't have a chance at life, especially after her powers were revealed as a toddler.
When Valkyrie cried, she would pull moisture from the atmosphere and create snow. She didn't know it, but she did. Her poor mother couldn't keep her powers from being revealed, but she could keep her in isolation her entire life, she reckoned. Valkyrie's father wanted to be rid of the babe as soon as her powers were revealed, and he found that his wife had known all along that her powers would be bestowed upon her at birth, he left. Valkyrie learned later of her father, and grew enraged at him. As a twenty-year-old with five children, including a son with snow-white hair and ice-blue eyes, she left her family to seek revenge on the father she'd never had. She found the man, ill, and froze his heart, instantly killing him. She, however, did not take care to hide her powers as she completed this dreadful deed. She was dragged into the town square and killed for practicing witchcraft, although it was not even witchcraft; it was ability.
Valkyrie's son was, ironically, the black sheep of the family. His siblings had dark red hair like his father's, and dark eyes. However, he was pale in all aspects of his being as well as the word. On top of his powers, which he found on his own, he started teaching himself of sorcery. He was sly and kept himself hidden, knowing all too well of the consequences of his powers being revealed. He had been five years old when Valkyrie had been murdered, and his grudge against all those who had killed his mother remained through his life. He was unable to seek revenge against anyone, however, and instead focused on learning how to control his powers.
He, Walfred the Stoic, was the first in a long line of magic-bearers that learned to control his abilities. However, he passed in battle before his last daughter, born during the war in which he'd fought and died in, could learn of how to control her own.
And so the cycle continued. One child out of each family tracing back to Valkyrie and her mother before her would be born with magical powers of ice and snow. Unfortunately, Walfred had not taught the extreme control and will that was necessary to control the powers if love was absent, so as the popular use of witchcraft and sorcery faded into nonexistance, they slowly became less capable of controlling their powers.
The Princess of Raghnall had two other sisters. Linnea and Ingrid. The trio were close and nearly inseparable as children; however, as time progressed, Ingrid became aware of her powers, and the dangers lying beneath them. She couldn't bear the thought of injuring her sisters, so she locked them out and refused to come in contact with them, so long as she lived. When the Princess of Raghnall married and became Queen of Arendelle, she prayed to all of the Norse gods, hoping she would not ever have a child with the magical wintry powers bestowed upon her estranged sister. But thus begins the story of Elsa, princess and future heir to the throne of Arendelle.