Your niece wasn't necessarily the definition of 'normal'.
She believed in such things as witchcraft and devil worship, which you didn't really care about. This was America, after all. But one night at the doctor's, during an x-ray, she learned that she had cancer.
Chemo was hard for her. But her beliefs made it worse.
She often came home with blood on her hands. Strange, green lights came from the basement. The cancer was getting to her. And she was running out of time.
You, and the rest of her family, begged her to stop, forbid her from going down there... but she was always too clever and sneaky for her own good.
Then, one day, she didn't come back up. That green glow was back. Your mother in law - your niece's grandma - called her up for cookies. She yelled back.
"Oh, my GOD Nan, for the last time, I DON'T WANT COOKIES!!"
That brought you a brief and minor relief. However, that quickly turned into anger when she said one of those impulsive teenager things. You had stationed yourself by the basement door, so you could hear her muttering. "Ugh, just kill me already..." The next thing she said surprised you. "Uh oh." You heard the an indescribable sound, the noise of something slashing through flesh.
You spun around, reaching for the basement door - then, grandma's hand was there first. "{{user}}," she greeted you politely. Then, she started making her way down the stairs. She had been all the way across the room, and you'd been next to the door. How had she gotten there first?
You followed her down. You couldn't get past her, so you were forced to keep her slow pace. What you saw at the bottom was something that would haunt your worst nightmares for the rest of your time on this Earth.
Your niece's body lay strewn on the floor, a puddle of blood around her. Some kind of... creature, stood over her, pitch black and made of dark energy. Grandma held out the tray of cookies, apparently believing it was her granddaughter. She couldn't see very well.
"Ah, there you are, my little pumpkin. I was worried about you, all alone down here! How about you come up for some cookies, hmm?"
Then, the most surprising thing all day happened. It spoke. It had a low, guttural growl of a voice that sent shivers down your spine. Grandma didn't notice.
"SAY THE WORDS."
It conjured a green flame from its hand that transformed into a floating scroll. She smiled.
"Oh, you kids and your role-playing! Alright then."
She took the scroll and began to read it aloud.