A Glimmer of Hope

Starlight was on the train home from Canterlot when the letter materialised in front of her, engulfed in emerald green flames. Twilight wanted her to know something. She read, her curiosity increasing with every word.

Dear Starlight Glimmer,

I am writing to you about a pony who has approached me this morning.

This mare, who wishes to keep her name hidden, says that she used to know you and wishes to meet up with you again. She met you a long time ago, and isn't sure if you will remember her. However, she thinks that you and her would enjoy some quality time together if you got to know each other again.

Don't come into the castle before one o'clock. There's another surprise that needs to be prepared!
Your friend and mentor,
Twilight Sparkle.

A pony? A mare from her past? Presumably, Twilight meant her dodgy past, when she was dictator of her village and made everypony equal by stealing their cutie marks. She frowned. No mare with any sense would want to meet her again. Then an impossible thought occurred to her.
What if it was somepony from BEFORE I started the village?

No. That was impossible. It was so long ago, even she had trouble remembering her life as a filly. Her best friend had always been Sunburst, then he went off to Celestia's School for Gifted Unicorns. She had run away to a far corner of Equestria and started the mountain village. No. She was missing something.
I WILL ALWAYS BE HERE FOR YOU, I WILL ALWAYS BE HERE FOR YOU, I will always be here for you...
She heard the Echo of the Past. She had studied them. That voice, it was her voice, when she was a filly. She couldn't remember the details, but somepony obviously had gone to Twilight asking for Starlight's help. The train wasn't far from Ponyville Station. She would find out at one o'clock who needed her. She had no idea what would be thrown at her. She knew it was a mare, but that was all. Presumably, the other surprise was a reunion party.

The train slowed as it pulled into the station. Starlight left, showed her ticket to a pony at the desk near the exit, and headed to the first place she could think of that she wouldn't bump into her friends: the cottage that Maud Pie rented.

Maud was in the back garden, which had had all of the rocks piled on the crazy paving and app the grass dug up. She was absorbed in her work, yet she wasn't startled when Starlight said, "Hey, Maud, how are you?"
"I am good, thanks," Maud replied in her monotonous voice. "And you?"
"I'm okay, I just fancied popping over for a chat. Do you need any help with this garden?"
"I would like to make something different," the grey Earth pony mused. She held up a few carefully drawn pictures. "I want to have some grass, with a cobblestone path and a fountain in the middle. I've had all the grass dug up so that I can rearrange it all but I don't know what to do next. I'm quite good at identifying rocks, but I can't do rock gardening that well."
"I have a couple of hours until I'm needed for any friendship problems, so I could help."
Maud smiled gratefully. "Thank you."

Starlight had a few ideas. Back when she had been dictator of her village, she used magic to make sure that everything was symmetrical and even. Here, though, fence panels were slightly out, so a symmetrical look was hard to achieve. Plants could stop that from being a problem and she had an idea how to make that work.
"Have you ever thought of growing ivy on the fences?" Starlight asked Maud.
"Ivy. That sounds nice. Does it need a lot of work?"
"All it needs once it's planted is a little water and a trim every so often."
"I could get some nice varieties. Then we could make something really pretty. If I use some string, I can get something sorted."

Three hours later, the ivy was planted and most of the cobblestone path was laid. Starlight checked the time. Half past one. Her friends and they mysterious mare were probably ready. She didn't want to leave Maud, but felt that her other friends wanted her.
"Maud, I need to go now," she told her friend gently. "I need to go see your sister Pinkamena and her friends. I'll come round with her later, depending on how long they keep me at the Castle of Friendship."
Maud smiled. "Don't worry, I'm not upset. You have really helped me today. See you later. If you can't get here today, come tomorrow. I'm not fussed." The friends hugged and Starlight left for Twilight's castle.

As she trotted there, she became nervous. She was unsure of what was in store for her that afternoon. She was also excited, though, because this had never happened before, and it was unlikely to happen again. She had butterflies in her stomach. This could easily be one of the biggest friendship tests she had ever faced, or one of the most enjoyable. Pot luck. Usually, pot luck did not work out how she wanted it to, but Rainbow Dash was flying around and clearing the clouds near the castle, so she expected it was the enjoyable kind.

She knocked on the door. Spike answered it and told Starlight, "Go through to the throne room. They're waiting." Rainbow Dash chose that moment to fly through the open door and disappear. She followed the stream of rainbow coloured clouds that had been left behind. Thr throne room was dark, as she expected.
"Everypony, I know you're throwing me a surprise party," Starlight told the ponies hiding in the dark, "now tell me who the mystery mare is."
The lights came on. From left to right, Applejack, Fluttershy, Rarity, Rainbow Dash, Pinkie Pie and Twilight Sparkle stood. No unknown mare.
"You promised," said a voice from behind Starlight, "that you would always be here for me. Here you are, Starlight." The mare walked around Starlight. Her coat was plum purple and she had a light red mane and tail. Her eyes were a very light blue. There was a severed stump where her horn should have been, and her right eye was scarred.
"Tempest Shadow," breathed Starlight before embracing the grown-up version of the filly she had met for one night and promised to help.

I WILL ALWAYS BE HERE FOR YOU, I WILL ALWAYS BE HERE FOR YOU, I will always be here for you...