Based on Argodaemons Remembrance. Also using Ashley H's audio Drama. Link to hers below. Have permission to do this as well.

Remembrance by Ashley H

Remembrance by Argodaemon

"Becoming a Alicorn wasn't the hard part. Its watching everypony you love die. Knowing you will never see them again."
For thirty years, these thoughts have haunted Twilight Sparkles mind. Thirty years to the day she lost the last of her friends.
Now, after coming across the Nightmare, a century after defeating it the first time. She comes to a realization with the help of the other princesses, if it gets a host. They cant stop it.
The elements of harmony, once bright beacons of light now lay dull, cracked and broken as she cant wield the last gift of her friends. A trip to Ponyville will lead Twilight back to the past. To help rediscover the elements.
But what if it's already too late?