"Mwahahaha!"
The shop owner was counting his bits then suddenly remembered something. "You aren't planning to use that on yourself, are you? It's very perilous. It's got Alicorn magic in it, so any normal unicorn that tries using it goes all evil and maniacal."
Trixie stopped mid-laugh. "-ha... Perilous? You mean I can't use this arcane artifact's vast power despite my having spent my life savings to purchase it?"
"No, no. You CAN use it, but it will just make you evil instead of misguided and maniacal-er than you are now." He continued to count his bits and then paused and looked deadly serious at her. "No refunds."
"But then what good is it to me!?" Trixie practically wailed.
"No idea. I only promised not to sell any perilous artifacts to any evil ponies. I've done my duty." He finished counting his bits and dropped them lovingly into the till.
Trixie frowned and a fell wind sprang up from the Pegasus pony on the scooter as she whizzed by. Suddenly, lightning flashed and thunder crashed from a mail pony kicking an errant cloud when one of her legs unexpectedly cramped up and a truly evil smile unfolded on Trixie's face. "I may not be able to use this perilous amulet... but I know someone who can!"
"Mwahahahahahahaha!"
The shop owner looked up and squinted at his maniacal customer, curious if he was going to need to use the ejection wards if she'd gone ahead and used the amulet despite his warning her not to. She was certainly maniacal, but her evilocity still only rated a misguided classification. He went back to trying to shelve another pink copy of the Neko-nom-nomacon, he'd gotten from that delightful baker from Ponyville.
"Citizens of Ponyville! Do not worry! The reign of the Evil Twilight Sparkle is at an end! For The Great and Powerful Trixie is here to save you!"
Hooves held high, eyes closed and a smile upon her face she was prepared for the impassioned cries of thanks and adoration from the clearly desperate Ponyvillians. The response she received was somewhat less than what she expected.
"Oh, Hi Trixie! What brings you to town?"
Eyes still closed and prepared to bask in adoration, she responded, "Trixie is here to save you from the most evil, dastardly, despicable, malevolent pony to grace this lovely and humble town."
"Save who from what now?"
"Twilight Sparke. Trixie, err, I am here to save you all from Twilight Sparkle."
"You're here to save us from me?"
"Yes, Twilight, I'm here to save you from yo--" Trixie's eyes shot open and ballooned to twice their normal size. "How long have I been talking to you?" Her eyes returned to normal.
"Since you arrived in town and parked your wagon in front of my castle." Twilight raised a hoof and pointed over Trixie's shoulder.
Trixie turned around gaped. "Castle! Yes, I see... There didn't used to be a castle in Ponyville, was there?"
"It's fairly recent. I got it shortly after my previous home was destroyed in a cataclysmic fight between good and evil. Well, the second to last cataclysmic fight between good and evil that I've been involved in, if you want to be exact about it."
Trixie was still staring at the castle adorned with Twilight's cutie mark. "So, somepony else already defeated you and removed the Alicorn Amulet?
"Oh, no, no. I'm still for the most part undefeated. A few minor setbacks, but I always win in the end." She rifled through her saddle bag and using her magic lifted a familiar amulet out and fastened it around her neck. "And speaking of that amulet, I assume I have you to thank for sending it me?"
A nervous tick played out in Trixie's equally nervous smile. "Why, whatever gave you that idea. Trixie has never even heard of the Alicorn Amulet before. And she most certainly doesn't recognize that you've fastened it around your neck and it appears to be glowing and also seems to be causing your eyes to glow with crimson power."
"Well, Muffins delivered the amulet to me when I was visiting Canterlot shortly after I became the Princess of Friendship. Despite the note stating it was a gift from the princesses, the hoofwriting wasn't familiar to me and neither Princess Celestia nor Princess Luna knew anything about sending it to me. They did; however, recognize the amulet immediately and we all had a good laugh."
"But why didn't it turn you evil?! It's perilous, after all." Trixie wondered aloud, momentarily forgetting she'd earlier feigned ignorance of the amulet; albeit, very badly.
"Oh, that was why we all had a good laugh about me receiving the amulet when I did. It only turns unicorns evil and I'm an alicorn now, see?" Twilight fluffed her wings up really big. "It was originally designed by Starswirl the Bearded to help new alicorns focus and control their powers. It was incredibly fortunate that I got it when I did, or some sticky situation that cropped up might have turned out very differently."
"Then, yes, Trixie was the one who sent you the amulet. You are obviously a hero and Trixie is also a hero by extension! Praise Trixie, give her your love and adoration, citizens of Ponyville, or your Princess of Friendship will smite thee from her tall and intimidating castle!"
Rolling her eyes only fractionally and sighing so it was only audible to emotavores, Twilight dropped her bubble of silence spell she had cast earlier and wrapped Trixie in a magical aura to float her along as she continued to walk to Sugar Cube Corner. "I'm going to buy you the most deliciously decadent ice cream sundae you've ever seen in your life, my closest friends will all thank you for sending me such a wonderfully useful amulet, and then--"
"Trixie likes where this is going," she said with a smile.
"--and then I'm going to lecture you about how inadvisable and downright dangerous it is to send powerful, undocumented, and perilous magical items to ponies who could be harmed by them." She paused and looked at Trixie with a raised eye.
"On second thought, Trixie does NOT like where this is going," she gulped uncertainly.
"And then, I'm going to throw you in my castle's dungeon."
"No! Trixie must have wide open spaces and adoring crowds or she shall surely die!'
"Just kidding about the last part. What kind of Castle of Friendship has a dungeon?"
"A friendship dungeon, perhaps?" guessed Trixie.
Twilight's hoof stroked her muzzle in thought. "Hmm... I'll consider it. Now, let's get some ice cream!"
"Hurray! Umm... Twilight?"
"Yes, Trixie?"
"You're not really going to lock me up are you?"
"Of course not. I just told you that I don't have a dungeon."
"Then what will become of the great and apologetic Trixie?"
"Well, Princess Luna wished to have a word with the pony who sent me the perilous amulet..."
"I think I'd rather have preferred the dungeon," the blue unicorn whimpered a bit.
"Don't worry, I'm sure nothing bad will happen. Who knows, you might become her personal student and have a guest spot next season."
"What!?"
"Don't worry about it. I've just been spending too much time with Pinkie Pie. You'll be fine. Pinkie Promise!"
End