Twilight continued to stare down at the stranger mare clinging to her like a lifeline, the one that had just called her 'Mommy'. "Uhh..." she began again nervously, unsure how exactly to approach this situation.
"Starlight," a stallion's voice called, gently if a tad nervously, from the house. An orange stallion Starlight's age stepped out, with green-blue eyes, white socks, a white mark on his muzzle, and a flaming orange mane, tail, and goatee stepped out of the house wearing glasses and - of all things - a green and blue star speckled wizard cape patterned after Starswirl's, minus the bells. "You really should have held back."
"But Sunburst!" Starlight whimpered, turning towards him. "It's Mommy! She's back..."
"It hasn't already happened yet, Star," Sunburst pointed out calmly, comfortingly.
Starlight bit back a sob. "Oh...r-right..." She pulled back from Twilight, managing to get herself under control. "S-sorry. I'm sure that...caught you off guard-"
"Eh, it was her turn for one of these shocks by now," Rainbow pointed out calmly. "Besides, she's used to time travel shenanigans with her family."
"Not when it gives me kids I don't know about!" Twilight pointed out defensively.
"Why don't you let me handle this, Starlight?" Sunburst offered calmly. "You go inside and play with Sunstar."
Starlight nodded slowly. "That...that sounds like a good idea," she murmured, turning and making her way back into the house. Soon, there was the sound of a few bells jingling...and a foal laughing?
"G...Grandchildren, too?" Twilight whimpered softly. "But...how-"
"I can explain it," Sunburst spoke up. "At least...as you explained it to me. T-though you didn't have wings then, Your Highness..." He began to stammer as his nervousness kicked in.
"None of that," Twilight chided. "We're...apparently family, so don't go tripping over my title, alright?"
Sunburst nodded. "We...I suppose the simplest way I can explain this is with a picture...or, a graph really." Stepping back, he drew two solid lines on the ground, marking them in black as the borders of the graph. Labeling them Delta and Theta, he then drew a green line arcing along the graph, only for a pink line to curve backwards, be intercepted by a purple line that completed the circle, and then led into a gold line that looped on itself around the pink and purple lines before continuing on along a slightly different curve from the original green line...though the lines other than the graph were drawn thick as he drew them with his hoof, coloring them with magic.
"You see...what we have here is a closed corrected quantum loop," Sunburst explained.
Twilight's eyes went wide as she let out an understanding 'oh'. The others, however, just looked confused. "In Equish?" Rainbow asked bluntly.
"This green line is how time went normally," Sunburst explained. "The pink line is your first encounter here with Starlight in the original timeline...when she'd created a cult about eliminating Cutie Marks to create true Friendship." Noticing the disgusted looks, Sunburst nodded. "Yes, I know. You all arrived and soundly defeated her...but she escaped, now obsessed with taking revenge on all of you. Reworking one of Starswirl's time travel spells, she used it to usurp control of the Everywhen aspect of the doors in your castle, letting her travel through time at will, determined to prevent the six of you from becoming friends by stopping Rainbow Dash's first Sonic Rainboom."
"Wait...she reworked a time travel spell to control an artifact of that magnitude?" Twilight gasped in shock. "But the level of technical expertise it would take just to understand such an artifact, let alone take control with a spell to utilize it remotely..."
"Starlight's always been a prodigy," Sunburst explained proudly. "This purple line is your pursuit of her, eventually discovering her reason for behaving the way she did was because..." His voice trailed off. "Well, she grew up in an orphanage, and I was her only friend. But when I got my Cutie Mark in magic, I was sent off to Celestia's School for Gifted Unicorns and...everything was so exciting and new..." He lowered his head, guilt pouring off every feature.
"You forgot her," Twilight concluded, "which is what led to her blaming Cutie Marks."
"According to you, that's what happened in the original timeline," Sunburst explained. "Apparently, your solution on seeing Starlight as a filly so heartbroken...was to adopt her as your own, use a spell to send your alicorn potential to your comtemporary self, and then raise her through history as a unicorn. You even enrolled her in Celestia's school once your own tutelage brought her to the point she found her Cutie Mark."
"But..." Twilight shook her head. "Setting aside the how of severing my alicorn nature to send to my younger self, doing so would drastically accelerate my aging process, especially with so many forms of time travel involved-"
"Which is what happened originally," Sunburst explained. "As you lay dying from age, Starlight and I...put together a way to fix it. We couldn't keep you alive...but we did figure out a way you could survive next time around. I've always been the book smart one of us, while Starlight's more intuitive...and has a great deal more power. I figured out which spells we'd need to modify, she figured out how to put them together..." He took a drink to clear his throat. "So we collected your essence on the moment of your death, and recreated the Cutie Mark Cult to lead you to here at the same time and place. That time, like this time, Starlight got emotional, leaving it to me to give you these two spells." Reaching under his robes, he handed Twilight to furled scrolls.
Unrolling them, Twilight examined them quickly. "This one uses the Mirror Pool to create a unicorn duplicate of myself to send back, keeping my relatavistic alicorn potential constant, and the copy would decay at the same rate as me severing my alicorn nature...and this spell creates a stable quantum loop allowing me to send myself back and then reabsorb my future/past self, as long as the reabsorption - with all the memories and shared emotional bonds - happens after sending my unicorn self back. These are incredible!"
"And we create them on our own each time, without input from you beyond telling us we got it right," Sunburst explained, "negating the bootstrap paradox."
"I...I can hardly wait to see her discover her talent," Twilight murmured excitedly. Turning, she dashed towards where they'd all arrived. "Spike! I need to go to the mirror pool!"