It was almost evening again by the time the Friendship Express rolled back into Ponyville with Sunset Shimmer and Aria Blaze on board, and by the time it slowed to a stop at the station the two ponies were locked in a rather vigorous conversation the likes of which they had never shared before. About Equestria, about the ocean, and about the Equestrian history that Aria had missed while they were stuck in the human world.
Aria was swimming through the air with her collar in place as they left the train station and turned towards Twilight's friendship palace. "Princess Luna seriously spent a thousand years on the moon? Sheesh, and I thought we had it bad in the human world. How did she not go completely bonkers?"
Sunset shrugged comfortably. "I don't know, can't say I've talked to her. When she got back I was in the human world too. According to Twilight she's at least more sane than you would expect."
"Which isn't saying much." Aria snickered.
The curious ponies who passed them in the dusty streets went ignored as they made their way up the town center to the crystalline castle, where they found Starlight Glimmer and Trixie sitting in the throne room with a massive book perched between the two of them. Their horns were glowing brightly with unicorn magic as Trixie chanted clearly magical words under her breath, though their magic faltered when Sunset Shimmer entered.
"Ah! Sunset Shimmer!" Starlight Glimmer jumped out of her seat and rushed to greet them. "And Aria Blaze. I was starting to wonder if you were coming back. I thought you'd be back yesterday."
"We had important business to take care of." Sunset smiled up at her sea pony friend. "Is Princess Twilight not back yet?"
"Nope, you managed to beat her back."
"Well, that's okay. I guess we'll just retrieve my necklace and be on our way, then." Sunset nodded.
"Ah, of course... that." Starlight Glimmer gestured for the two of them to follow, then turned to lead the way down the hallway towards the back of the palace. "That rock of yours is a heck of a thing, as it turns out. I've been keeping it in the palace for the last two days just so there was no chance of it destroying the town."
"Destroying the town?" Sunset Shimmer's eyes shot wide open. "Are you serious?"
"She's exaggerating." Trixie waved her hoof. "She just got freaked out by a measly little earthquake."
"An earthquake?" Sunset Shimmer gaped.
"See Trixie? That's how you react to an earthquake." Starlight nodded in satisfaction as they reached one of the back rooms and pushed the door open. "Don't worry though, we've kept everything under control. Especially since Maud refuses to leave the rock alone." Sunset Shimmer stepped into the room to find Maud Pie peering through a microscope at the familiar glowing red stone on a string. There was a less shiny rock sitting on the table close by, on top of a pad of paper. "Hey Maud, it's time to give the rock back to its owner."
Maud looked up from the microscope. "Boulder is going to miss her."
"Her?"
Maud nodded. "Yes. Maggie and Boulder have become quite close."
"Well maybe they can visit later, Maud. We're not keeping it." Starlight smiled wryly. "Now come on, give it back."
Reluctantly, Maud rose from her seat, set Boulder back into the breast of her dress, and brought Sunset's stone back to hand it over to her. "Take care of her for me."
"I'll do my best." Sunset Shimmer slipped the necklace back on with her magic. "Did your studies yield any results?"
Maud nodded. "Yes. I wasn't able to do every test, but as far as I can tell the rock is made of pure Magicite."
"Magicite?" Sunset Shimmer raised her eyebrow. "What's that?"
Maud shook her head. "Nopony alive today really knows. We do know its primary function is to amplify or enhance magic, and it's one of the primary components of all of the most powerful magical artifacts currently in existence today. The Alicorn Amulet, the Bloodstone Scepter, and others all owe their potent magical abilities to this substance. Or perhaps, they amplify an ability the wielder already has. As I said, nopony really knows."
"Holy crap..." Sunset Shimmer put a hoof over her stone. "If it's that powerful, why are such artifacts so rare?"
"No veins of Magicite have ever been found. Its origin is a mystery, and not a single pure sample of it has ever been seen in recorded pony history." Maud blinked slowly. "So you can understand my excitement."
"Yeah, I'll say. This is a heck of a find, isn't it?" Sunset Shimmer cast a swift glance at Aria. "Hey, do you think the Siren Stones were made of this stuff too?
The sea pony's eyes had fixated themselves on the stone, almost as if giving their own soft, ruby glow in response to it. But the transfixed look in her eyes faded so quickly that Sunset could have simply imagined it, as she met Sunset's gaze and lifted her head into the air with a careless shrug of her fins. "I dunno, maybe, don't care..."
Maud continued. "If it wouldn't be too much trouble, I would like to look at the cave where you found these rocks. There could be some kind of clue to their origin there."
"Sure, we'll have to set something up." Sunset Shimmer nodded. "For now I've already skipped one day of school, and should try to focus on that for a while."
"Then don't let us keep you." Starlight Glimmer gestured to the door and turned to lead the small group towards the mirror room. "And do feel free to come back any time. Princess Twilight left specific instructions for us to entertain you whenever you appear."
"Thanks, but I'll try not to abuse the hospitality." Sunset Shimmer approached the mirror with Aria, then slipped off the sea pony's collar with her magic and passed it back to Starlight. "And here, hold onto this. In case you need it again here, because we don't need it there."
"Will do." Starlight gave a swift salute. "Later."
With that, Sunset Shimmer and Aria Blaze moved through the mirror back to their new home world. Sunset was glad to have bonded with the former siren, there was a sense of camaraderie and comfort that simply hadn't been there before.
Though for some reason, Aria seemed to be avoiding looking directly at her... perhaps she was just nervous about their blooming friendship.