To be honest, I'm not even sure what this is. I completely just made it.

Trigger warning: mentions severe mental health, death and problems with family/ friends.

Y/n Stillinski was a dark matter and not the scientific kind.

"Isn't it strange Stiles?" Y/n says wondering aloud.

"Is what strange Y/n?" Stiles replies.

"Its so strange that Autumn is so beautiful; yet everything is dying." Y/n concludes to younger brother Stiles.

Y/n is four years older than Stiles. They were really close but when there mother died it exhausted the flame in Y/n. She stopped being close with many people, not just little brother Stiles. She stopped being close to her dad, to her best friend Jordan Parrish, to boyfriend Derek. One day, in Autumn, Y/n left. She was fourteen. Y/n did not return until she was nineteen, three years ago. Y/n left on the year anniversary of her mother's death. She would not talk about her time away from Beacon Hills, yet said it was voluntary to leave. Y/n hasn't been the same since she left, since her mother died.

When she returned, her and Stiles fell out big-time but they healed quite fast with each other. Y/n does not actually live in Beacon Hills anymore, she lives five hours away but she comes back, every Autumn, every year, for thirteen days. Y/n has not spoke to Derek since she left all those years ago when the two were fourteen. She has been too afraid. Derek has been too heartbroken and the pack only knows because when Y/n came home three years ago Stiles and Scott told everyone. Derek refuses to talk about Y/n, but he has not dated a single person, nor kissed, nor done anything further with a girl since Y/n. Derek told Isaac once that this is because technically the two never broke up and he is determined to stay loyal to Y/n.

"Wow, Y/n. Way to lighten the mood." Stiles says sarcastically, trying to do so himself.

Y/n whips around in the crisp Autumn air, "Stop being so naive Stiles. The world eats up kids like you."

"Okay, I'm sorry." Stiles says, upset.

He doesn't understand why Y/n so drastically changed, why she's always mean. Hours later, Stiles is still wondering and he's called a pack meeting to discuss how to help his older sister.

"I-I've never seen someone with such crippling depression." Lydia says quietly.

"It seems like she is still grieving heavily for your mum, Stiles. However, I think it's more than that." Scott says smartly.

"Trust me, I'm still grieving for my mum too and dad is too but I do not understand why she left, why she is like the way she is now." Stiles vents to his closest friends.

"I thought you had this conversation when she returned?" Kira asks.

"We did. But I've still got questions. We more had an argument but we never properly discussed it. We haven't particularly got on since before mum died." Stiles replies.

"Why don't you just asked her?" Isaac suggests.

"Its not that simple with Y/n I'm afraid." Malia says, upset.

Malia has always been close to Y/n, her and Derek are cousins. Y/n and Derek got together when they were ten.

"What about her?" Derek says walking in, stone-faced.

"D-Derek, we were just discussing how to help Y/n-" Liam starts.

"I don't want to talk about her." Derek says, still showing no emotion.

"But Der, you could really help us help her." Malia says.

"We all know how you feel about her." Jordan pipes in.

"How long have they been together?" Kira asks.

"Ten years this October thirty-first." Derek says quietly.

"We can all see it in your eyes Derek. Do it, for her." Jordan says.

Derek agreed.

It took them another ten years to do so, but they did it. Y/n now stays living in Beacon Hills with Derek. She is happy and healthy and has started to see a therapist three times a week. She talks now, talks about stuff. Stiles finally got his answer as of why she left. It was twisted and it did hurt a lot of people but it was the truth and how Y/n felt at the time but she was crippled with mental health issues and tried to do it to protect her loved ones.

Y/n now has new loved ones to protect but not in her old, self-destructive ways. On the day little Dahila Claudia Talia Hale was born - October 31st 2029 - Stiles received this photo and a note on the back which read:

The last gem to save me has arrived.
Dahila - dark flower.
Claudia - after mum.
Talia - after Derek's mum.
We will always remember Stiles and that's okay. Dahila will remember too.
Love you Stiles.