The Solar Tyrant? Surely, they mean some other solar princess, maybe the inheritor of Celestia's powers. She never had the nature to be truly cruel. Even when she dealt with Discord she was still unable to finish the job and simply encased him in stone.
"Start with most complete. Beginning," Nightmare Moon suggested. She looked to Sunny who nodded.
The elder rubbed his chin then turned to face the other thestrals and whisper to them.
"Well, the oldest tale we have is known to us in song, so we--"
Nightmare Moon put a hoof on the thestral's face and looked at him with wide, unblinking eyes. "Sing and I will kill you," she said with an unswerving expression and calm voice.
"But we only know it in song! We don't know how to recite it otherwise!"
Moon's eye twitched. This was followed by her pacing around, grunting and groaning angrily. She looked to the crowd and wanted to say something several times but couldn't bring herself to speak. Eventually, the mare stomped on the ground with one hoof while Sunny looked at her with a deadpan expression. He and the others were startled when Moon smashed her head into a tree, tearing off a good chunk of its trunk.
"Fine! Sing! Just be quick about it!"
The elder cleared his throat, and with the others, began a long chorus that Moon was sure she was going to dread.
The radiant one, looking down with conviction
Raised weak foals with an iron hoof of her own
And as they grew she would cheer them on
Forcing her belief down their gullible throats
Her light warmed their bones
Her warmth fed their thrones
And with a radiant smile and heart like the sun
They fell for the tales she spun
Their numbers grew but so did her hate
The blaze of her eyes was ravenously great
Leaving them all to their fiery fate
And as they cried they turned eyes
Praying to the blazing star in the sky
But their prayers only fueled her hate
“You ignorant fools will never escape”
They would hear from her cries
“This world will be your scorching wake”
She would curse their demise.
Her rage, her hate, her smoldering gaze
Set everypony’s heart ablaze
And from that rage and from that hate
An infernal new Sun would arrive at their gate
Their homes burned to a crisp
Their cities returned to embery wisps
Oh what a cruel fate’s twist
That their fate would lie
In such a wrathful eye
This cruelty they could no longer deny
They begged for the respite of the calming moon
They prayed that nighttime would fall so soon
Yet nothing remained of that blissful dream
From the Sun’s unending beams
“You won’t ever escape nor will you hide”
The skies would infernally chide
“My light will find you till the ends of the earth!”
They cowered as they witnessed the Solar Tyrant’s birth
Her coat of snow burned away
Brimstone and fire were all that remained
And the aurora that once was caught in her mane
Vanished to ash beneath the rage-fueled flames
Her eyes once full of loving light
Now held the fury of Hades’ freight.
And her smile once comforting and sweet
Turned bittered and sullied within a heartbeat.
Their once fertile lands brimming with life
Charred in the Sun’s endless strife
And the lakes and forests that held beauty untold
Were now reduced to deserts and a barren world
And once the land was fully devoured
It turned reflective and glowered
Down the heat from the heavens above
Eternally depleting its once fertile love
Yet still in their infernal path
Beneath the volcanic castle of her eternal wrath
Her once loyal soldiers, citizens, and all
Found new courage against the Tyrant of Sol
Their loss were too many, burned by her light
Mortal against God, what an unwinnable fight!
Still they would not wane nor would they falter
Her heart alone, their advance would not halter
The darkest dawn
The many lives that we mourn
Could no longer be forlorn
As they witnessed a new hero born
The hero was fearless, battle hardened, and strong
He stood up to the Tyrant when the time had come
Hoping to right what once went wrong
Marching along to the beat of their drum
The grueling fight dragged on and on
However, in the end, their tenacity had won
The tyrant was broken, battered, and fractured
Laying in chains forever to be captured
“You think you’ve won?”
The Tyrant desperately cried
“You wretched kind will not escape my Sun!”
Were the last remnants of her hateful pride
As they watched their Tyrant depart
One thing remained heavinly on their heart.
As they looked at the hero, wounded and broken
An unknowing truth between them was spoken
To save the hero from death’s door
They pooled their magic into one last roar
And from their powers a new villain was born
Transforming their hero into another alicorn
Yet this new villain vowed and swore
To right the wrongs its predecessors bore
To rid the world of pain and blight
It promised to shine a new hopeful light
Their first night finally had come to pass
Alas, still this was not to last
For once the moon had crossed the horizon
The wrathful sun would once again have risen
Its rage and wrath could never be quelled
Cursing all the ponies that dared to rebel
It’s blinding heat forever a stain
Forever a mark of her vicious domain
The alicorn of light is no longer with us
Yet its wrathful companion is still as treasonous
Its heat will forever burn bright
Cursing us all with its infernal blight
Still fear not and do not fret
For there is respite from this horrid threat
The loving moon and its beautiful face
Will forever shield us in its calming embrace.
"What a lovely story," Sunny applauded.
Moon seemed furious. In reality, she couldn't figure out what to feel about all of it. Her sister turned into some kind of rock monstrosity of fire? Chasing after the ponies she loved so much. Impossible. There must have been something else hidden within the song itself.
"I want a copy of that song now," she ordered Sunny. He was quick to share her orders, and several thestrals left into the trees.
"Is something wrong, princess? At least now you know about your sister," the unicorn said with a nervous smile.
"No, I don't. She would have never done everything that they mentioned, it's impossible!" she shouted. She dragged a hoof across her face. "I need to read that song. There must be some hidden message within it." She paused a moment and looked to the thestrals that had presented themselves to her in the castle. "Who is the 'hero' in the story?" she asked.
"I...No pony knows for sure, actually," Cuttin' regretted. "The tales are really old, and there's a lot that gets changed as time goes on since we still forget a lot?" She shrugged. "After a while we apparently just start filling up the blanks with other tales we already know and remember."
The alicorn bit her hoof in frustration, exposing her massive fangs for all to see. Some seem a bit more enthused to see them than others.
"Do you have any other tales concerning this 'solar tyrant'?" Nightmare asked.
"We only have a few, and most of them are incomplete, like I mentioned before."
Moon nodded. "Tell me one you like," she said.
Normally, Nightmare Moon wouldn't care about the whims of the peasantry, but this was vital information. Thinking about the song, she realized that the mountain Canterlot was built into had become a volcano. A vital clue for certain, and if Celestia had truly turned into such a monstrosity then the glass the alicorn had seen earlier would certainly be more apparent and spread across a wider surface, unless the ancient ponies dug everything out.
Cuttin' grunted as she recollected everything she knew. "There's the tale of her saving a village then coming back to raze it."
Moon raised an eyelid. "Explain."
"Well, the village was suffering from a draught. Everypony was suffering and the foals were crying because they were starving and parched. Then the white alicorn came accompanied by her glass familiars."
"Glass familiars?" Nightmare Moon thought. These tales were estranging her more and more.
"They brought water and food to the village, and the white alicorn berated and punished the sun by pushing it further away. Then pegasi came under her supervision and brought rainwater with them. The land that had been cracked and broken for so long was now healthy and bearing lots of food. She came every so often to make sure the village was okay, and the villagers came to see her not as their ruler, but as a member of their family."
Nightmare Moon was disgusted. That sounded exactly like her sister. Sappy.
"Then, suddenly, she stopped appearing. The villagers thought that she was just busy, as her position made her appearances complicated. It was always a miracle that she could come to begin with, but then...the sun started pushing through the clouds once more. The villagers believed it to be angry, and its vengeance was slow but constant. It burned away not just the land, but their homes and their own bodies. They hoped, desperately that the white alicorn would arrive to save them as before, but she never came."
Moon frowned. More oddities in her sister's behavior, if this was even her.
"Then somepony came. A few of them. They were battered and wounded, and even with their own suffering and limited resources, the ponies welcomed them to their homes and soothed their ailments to the best of their ability. And then she came. Her teeth were bared and her eyes wide, she stomped in, yelling at the top of her voice, every syllable making the world shake in fear. She demanded that those she had chased be returned to her and they wouldn't escape for defying her. The villagers refused, saying that the white alicorn would come and save them, but the solar tyrant laughed at them and said that she was that loving alicorn. The village was destroyed by her and her glass familiars while she looked for the fugitives." The thestral pursed her lower lip. "They found it strange that she destroyed everything in her path but ignored the villagers, but, now the villagers had nowhere to live."
She paused and looked up at the alicorn with a smile. "And...this is your favorite why?"
"When she was pushed back, the hero and the others came and rebuilt the village. It was left vacant under the fury of the sun while the solar tyrant was suppressed, and after that, everypony had a home to go back to, and the village became much bigger than it had been, so the family grew exponentially."
"Right..." Moon spat as she looked away. "Any others?"
Every tale shared seemed to be the same. Some made sense, like the solar tyrant suppressing everyone and imprisoning them when she suspected them of something. Others she executed them. In others, the alicorn of the night stopped her. Impossible considering she was imprisoned at the time, unless a new one had appeared. In some form, the most extravagant always involved one or more alicorns standing up to this 'Solar Tyrant'. In fact, one such tale made mention of six ponies standing up to her and destroying her outright with magical artifacts, but that sounded far too ridiculous to be believable. Others brought veritable books turning the tale of the solar tyrant into fantasy novels that were very popular among the thestrals but not so much outside their little fruit-munching circles. The alicorn wondered if the other parts of Equestria, outside the dullahan, were aware of the existence of said Solar Tyrant as anything but a story or were even aware of it at all.
However, every tale had something in common regardless of the age it was or when it was made. She gestured to the thestrals to leave her be for the time being. It took Sunny's intervention to make them understand that she needed time off.
"Don't take too long, alicorn of dreams. We're going to have a great celebration to celebrate your arrival!" Mango announced enthusiastically. "The night in the day has finally happened, so there's no way we won't celebrate this amazing occasion!" He squeed. "In the presence of our very own goddess, no less!"
Moon groaned and shook her head. "These thestrals are a bit too enthusiastic about my appearance."
Sunny bobbed left and right. "Well, you have to understand that you're literally a figure of legend to them that became a physical reality. Anypony would be going crazy," he explained.
He was met with several nods. "Very true, servant. Still," she wheezed.
The unicorn was getting tired of hearing her call him a servant, but he couldn't really do much against it, and he really was one in the best of circumstances all things considered. "Is there something wrong, y-your highness?"
The alicorn dug through all the information she received, and her whole body seemed to tense up. "Did you notice anything in common with the stories?" she asked him.
The stallion looked around, too afraid to answer. "Aside from the solar tyrant, not really? She acted like a literal tyrant and--"
"Exactly!" Nightmare Moon blurted. "She would never behave like that, and it wasn't that she was behaving like a tyrant. In the majority of those stories she was said to have destroyed everything around her but the ponies themselves were harmed, but the amount was always less than it should have been, even with all the executions."
The alicorn tilted his head and looked at his ruler quizzically. "What are you getting at?"
"She was looking for something," Nightmare Moon said sternly.
"Well, of course. The rebels who defied her," Sunny said matter-of-factly. He jumped in fright when the mare stomped her hoof down.
"No, you idiot. Her words. They were always the same, and if these stories are fully or at least partially based off of that song, then yes, that would be just a coincidence, but these thestrals think that they know which is which. If that is true--"
"Why is this so important to you?" Sunny demanded. He quickly realized whom he was talking to and shrunk down. "Y-your majesty," he squeaked.
She was glaring at him. "I have reason to believe that this so-called 'Solar Tyrant' is my sister."
Sunny paled whiter than he already mostly was. "What."
"I had the same reaction, but this goes completely against her nature." She started gnawing on her hoof. "She was looking for someone or many someones, but why she was so deadset on finding and destroying them is a mystery." She looked to the side and snorted. "As does this hero they all speak of." She spat and stomped the floor. "I have to get more information," she blurted out immediately. "But at least now I know that Canterlot became a volcano. They are old tales but the best sources I can go off. If I can get a map or be directed to the nearest volcano I might be able to find the archives within. Maybe they'll elucidate what happened."