Luna soon returned to Canterlot and reentered the castle, heading towards the throne room. When she made it back, she saw Celestia sitting on her throne reading a scroll. "Luna, did you find out what you needed to?" Celestia asked.
"Yes, a memory that belonged to Moonstone has awakened inside my mind," Luna answered.
"A memory? Of what?"
"Moonstone's room and the reason for my tears: the shards of Sunstone," Luna responded.
Celestia walked over to comfort Luna and asked, "Is there anything I can do to help you?"
"Tell me, has there been any memory that you have had that is unfamiliar to you?" Celestia knew what Luna meant by her question and knew she would be disappointed with her answer.
"I'm sorry, I'm afraid that I have none of Sunstone's memories," she replied.
"Do not worry, I already know how you can help me. At nighttime, I want you to come with me into the dreamscape. I have a strong feeling that her memory is more than meets the eye. If we observe the memory, maybe we can learn more about it."
Celestia then nodded and said, "Very well, I will do what I can to help. For now, you should get some rest." Luna proceeded to her bedroom and began to sleep until sunset.
Inside her dream, Luna began searching for the door hoping there would be something else that would help her and Celestia find out more about the memory. She found the very same door and opened it the same way and headed towards the shattered gem at the end of the room. When she reached it, as expected, tears started to stream down her face. Luna tried to ignore the tears and began inspecting the shards more carefully. She tried to place her hoof on the bubble, but instead, her hoof phased through the bubbled shards. As she retracted her hoof, she started to hear the sound of approaching hoofsteps. Luna turned around to see a unicorn with a silver coat, a light blue mane and eyes, a grey gem with a blue highlight on her neck, and no Cutie Mark. Just like Luna, tears started to leak from her eyes and run down her cheeks. She continued to walk towards the bubbled shards while passing through Luna. She stopped in front of the bubble and looked straight at it and continued to cry. "Sunstone, I broke my promise to you and look at what happened."
"A promise? What promise?" Luna started asking even though she knew the gem in front of her would be able to respond to her. Before she could learn more, Luna wakes up from her dream and gets up from her bed just as Celestia enters the room.
"Luna, it is time. Are you ready?" she asked.
"Yes, I feel more than ready," Luna responded as she and her sister went ahead to bring the night. After the two princesses proceeded to a balcony to bring about nighttime so their subjects can rest for the next day, they had made their way to Celestia's bedroom. Celestia fell asleep in her bed while Luna began to channel her magic and connected herself to Celestia's dream.
Inside her dream, Celestia found herself in a starry setting filled with different doors. "Welcome to the dreamscape, my sister," Luna said as she descended next to her sister. "Come, the door to the memory is just ahead." As the two sisters make their way through the dreamscape, they eventually find the door. Luna, like before, placed her hoof on the door which caused it to open and stepped aside to allow Celestia to enter first. As the two entered, they continued to walk through the room all the way to the end to where the bubbled shards are. When they reached the end of the room, Luna started to cry again but less than usual.
'I must be getting used to seeing this memory. It's losing the impact it had on me the other times,' she thought.
Celestia then turned to Luna and asked, "Luna, what do we do now?"
"I know what will happen next, let us just wait." A few minutes later, the door behind them opened with Moonstone walking in crying. Celestia tried to speak with her, but was stopped by Luna placing her wing in front of her and shaking her head. Moonstone continued to walk and stopped in front of and looked straight at the shards like before.
"Sunstone, I broke my promise to you and look at what happened," Moonstone said.
"A promise?" Celestia asked.
"If only I had protected to you, then..."
Celestia looked down with a sad expression and tears in her eyes and said, "Moonstone, it's not your fault. I don't blame you."
"Sister, what did you say?" Luna asked. Celestia then realized what she just said.
"Luna, I believe a memory that belongs to Sunstone as awoken." Just then, a light just shone in front of the sisters which caused them to shield their eyes with their wings. When the light vanished and the two alicorns opened their eyes, they found themselves in an entirely different location. As they looked around, they saw that they were in an open plain with a few flowers and trees around.
After a few seconds, they started to here someone else's voice saying, "I... I'm sorry. I swore to stay by you and make sure you didn't shatter. It should have been me." Celestia and Luna then looked past a few trees and bushes to see Moonstone with another unicorn with a golden coat and eyes, a long bright yellow mane, and a yellow gem on her chest area with a large crack on it.
The yellow gem pony's body started to glitch and she had a droopy horn, outstretched legs and a glitchy voice when she spoke, "Moonst-tone, please, d-don't be-e sad. I'm gla-ad you're st-til alive. Please, t-take my place and-d maybe we'll meet-t again somed-day." Just when she finished, a few more tears leaked from her eyes before the crack in her gem grew bigger until the shards fell apart and her physical form exploded into smoke. After the smoke had dissipated, the shards fell to the ground. Moonstone had a devastated look on her face as more tears started to run down her cheeks and as she started to gather all of Sunstone's shards. Once she saw she had all of them, she sealed them inside one of her bubbles and took it with her. As she was leaving, both Celestia and Luna were crying and started to hug each other.
A few minutes before time for sunrise, Celestia woke up and Luna stopped her dream spell. "Sister, was that the memory you received?"
"Yes, Sunstone's last moments, Moonstone made a promise to her to protect her with her life. To Moonstone, Sunstone was more than a leader, she was an inspiration."
"An inspiration?"
"Sunstone's knowledge of how Moonstone viewed her came with the memory. I should let Twilight, her friends, and the gems know about what we've learned." Luna nodded in agreement and the two then walked to the balcony to lower the moon and raise the sun. Afterwards, Luna went to bed while Celestia began writing a letter to send to the group at the temple about Sunstone and Moonstone.