She was born in a "crazy" family, resuming her mom was lacking in a day when she met a guy, she didn't know it a lot about him but that day was special... Some days later she discover that she was pregnant and the guy who was the father was "gone".So she decided to have the baby even having to take care of it alone.
During her pregnancy it was everything great, just sometimes she felt il.
When the baby was born it was Halloween, she decided to call the little girl "Emily", she was really cute and lovely.
Time had passed by and Emily was almost making 20 years old, and her mom was too seek almost dead. It was October 30 and they were preparing the house for Halloween, for them Halloween was the best date of the year because it was Emily's b-day and a "Holliday", the decor was really amazing every single year.
Everything was fine till the other day (31), in the evening a guy invaded her house and killed her mom. Emily thought it was a prank of her mom because of the date.. But in a few minutes when the guy was almost done with her mom she realized that it was an assassin and he had killed her mom.
She run away the most fast as she could but all the doors and windows were locked. The guy come into her and start to cut piece by piece of her body.. After she was dead he got her body pieces and gave for some dogs to eat, then no one would know about what had happened.
Well neither Emily and her mom knew it that her dad was the demon.. Emily discover it and got really surprised but she didn't knew what to do. The demon said to her that she can go back to earth again and have her life.. But she opted for staying there and only in Halloween nights she was going to the earth again.
So that is it, in every Halloween night she come to earth and help people (killing them) that is suffering for something like she was when she died...
And why killing not saving?
Well she can't save people because then she will be a hero and her father was the demon so she can't save people, but killing them is better than suffering like her when the guy was cutting her piece by piece, the pain that the person is going to feel when someone is cutting is worst and terrible so at list when people are in this occasion they have the chance of die without feeling pain.
And how does she kill?
Emily appear only for the person who is almost "dead",BUT BE CARERFUL SHE JUST APPEAR IF THE PERSON ASKS TO DIE!, she ask if they wanna end up with all of that fast, if the person agree with her, they just have to close the deal so the person have to kiss her.
To resume the facts Emily was born and dead in the Halloween night, then when she was dead she decided to be a "nice" girl. She was daughter of the demon, she had a little more advantage of people that is born from normal parents, and started to "help" people in Halloween night.