Narissa is the sister of Magus Medivh and daughter of Aegwynn and Nielas Aran.
Aegwynn decided that she would have a child to pass on her powers to.
During the birth there was a terrible storm of dark magic which split the child into two halves, Medivh the evil half with his dark magic and Narissa born as the good side.
Aegwynn did not want Medivh to find out about his sister because she thought that he would try and turn her or take her powers. So she brought Narissa to the Dranei leader The Prophet Velen to look after her.
Velen had a young Dranei couple raise Narissa into a High Priestess so she could learn to channel her powers.
Narissa had realized that she wasn't like the rest of the priests and priestesses because she found she had the ability to teleport and summon and appear to her fellow allies. This made her fellow people shun her and cast her aside because she was different.
She then started asking around of where she came from because she knew that there was something her drenei parents were not telling her.
She one day found her way to a meeting with The Prophet Velen. He then decided that she was old enough to know her past and told her of her past.
She now spends here time among a guild of fellow adventurers disguising who she really is in order to not reveal herself to her dark brother Medivh.
She knows that one day she will have to meet with him but until then she wants to live a normal life.......
Among her new friends which was something that she has not had experienced before.
Note:Yes I do know that Medivh is not evil but he is my favorite person in WoW lore and I wanted to include him in my background.