Dinky is writing a letter to a special somepony that cared for her, throughout her fillyhood. Stopping an important breakthrough, she writes this letter in all the memories she could remember from her and her mother being together.

Trapped inside the library.
An army of the flesh eating undead surrounding them.
Their town destroyed.
Twilight, Rainbow and Applejack spends what could be their last days, protecting each other.

She's dead...that's all I admit....true...I did horrible things in the past...sometimes I wonder if I even deserved to teach such a innocent and open-minded child...

She almost seemed invincible when she defeated the many enemies of mine...every time Equestria or I is threatened she would come...

She was so powerful....so wise...so faithful....

Now she's gone....and all I have left of her is her Letters...

I'm Princess Celestia.....and I mourn for Twilight Sparkle...

This story is a sequel to The Promise of a New Day

Story three of Savage Skies:
All sorts of things are brewing in the pegasus city of Cloudsdale, which is a problem for Ponyville as the one thing that isn't is a rainstorm. As the drought continues to drag on, Rainbow Dash must confront her hometown and its history, as well as her own history. But she won't do it alone, which is good, because she'll need all the help she can get.

Series starts with Foal of the Forest.
Now with a TV Tropes page.