The Winchester men, John, Dean, and Sam have been put through hell ever since their wife and mother, Mary was murdered by a demon. They have been hunting down every evil supernatural thing, hellbent on revenge. They have been trying to track down the demon that took Mary away from them. But what they didn't seem to understand was that everything that has ever happened to them was fated.
They also didn't know that they had someone very special watching over them. Her name was Iolanthe Jasmine Potter Black, she was also a one of a kind immortal creature known as the Mistress of Death.
You see, centuries ago Iolanthe's ancestor Ignotus Peverell, alongside his brothers Antioch and Cadmus outsmarted Death. They cheated Death when they conjured a bridge over a river that would have caused their demise.
Antioch, the oldest brother was an arrogant, power-hungry man who wanted to be unstoppable so he demanded Death give him an unbeatable wand. So, Death fashioned a wand from a tree. Soon, Antioch became drunk on the power and was murdered and so, Death claimed the oldest brother.
The second brother, Cadmus who was also an arrogant man, decided that he wanted to humiliate Death, asked for the power to recall others from Death, and so Death gave him the Resurrection Stone. Cadmus returned to his home with the stone and used it to revive his dead lover. However, he soon found she had not been truly revived; she appeared sad and cold, and Cadmus felt as if a veil still separated them. He was driven mad with longing, Cadmus committed suicide so he could truly be reunited with his lost love.
Ignotus, Iolanthe's ancestor was the most humble and wisest of the three brothers, hadn't asked for something to further his own desires, he requested the power to hide from Death. So, Death gave his own Invisibility Cloak to Ignotus. He went on to live to seventy-six years dying on May 19, 1292, in his birthplace of Godric's Hollow. He left the Cloak of Invisibility to his only child. His son. The Cloak itself was passed down through the Potter bloodline until Iolanthe received it.
After a rather nasty war, Iolanthe found she couldn't die so she decided to make the most of it.
Iolanthe started paying attention to anything strange all over the world and after she discovered that there were normal humans killing off every kind of creature that was killing normal everyday people, Iolanthe decided to open a department in the Department of Mysteries dedicated to helping Hunter's do their jobs and get paid for it and also, she funded a Health Insurance company for Hunters because it wasn't like they could go to a normal hospital and explain how they got their injuries.
Iolanthe made it her duty to watch over Hunters but the only ones who broke through the walls around her heart were the Winchester men. She tried not to but she loved them.