The days had passed, and Celestia, Luna, and Star Swirl had come no closer to discovering the secrets behind the Insidiosus Diabolicus. It was of no surprise, since this entity had remained concealed for millenia. The only noteworthy lead had been the death of Nostrildamus. Celestia had awoken one night in a cold sweat. The ancient Earth pony's ghost stood at the foot of her bed. It had mouthed something to her, smiled, bowed, and vanished. She had been so frightened that she hadn't made out the first word, it had been: something-hooves.

Star Swirl and Luna had been tasked with investigating the murder and the clue the ghost had given Celestia. They did not make much progress though, and the day had finally come for Mi Amore Cadenza's and Shining Armor's wedding. Tensions ran high, but the ceremony was proceeding without any sign of interference from evils, and/or Twilight Sparkles.

Princess Celestia performed the ceremony. "Mares and gentlecolts, we are gathered here today to celebrate the union of Princess Cadence and Shining Armor. The strength of their commitment is clear. The power of their love, undeniable. May we have the rings please?"

Spike, Twilight Sparkle's baby dragon servant, held up the rings Celestia used her magic to slip the rings onto Shining Armor and Cadenza's horns. "I now pronounce you mare and colt."

The wedding hall erupted into thunderous cheers and stomping of hooves as Shining Armor and Cadenza kissed. Celestia breathed a sigh of relief and winked at Star Swirl, who was watching the ceremony alongside his adopted niece, In Hoc Signo Vinces. With Dawnfire unable to accompany her, and knowing her own horn glowing would be a little obvious if she tried to cast the illusion herself, she had been forced to wear her armor to hide her ghastly appearance.

Thousands of ponies had traveled from all over Equestria to witness the wedding. The Canterlot Castle grounds were filled with the joyous ponies, and the noise was almost deafening as Shining Armor and Cadenza walked out onto a battlement before the masses and kissed. Rainbow Dash took off into the sky, accelerating to that magical speed and provided a sonic rainboom as the grand finale to this wondrous event.

Twilight Sparkle was so happy for her brother that she cried tears of joy. She watched him kiss his new wife and whispered, "Yes!"

Celestia looked at the look of joy on Twilight's face and smiled.

Fluttershy nervously touched Celestia's wing. "Um, excuse me, Princess. May I please talk to you?"

Celestia smiled at her. "Of course, Fluttershy."

The two walked away from the others. "What do you wish to speak with me about, Fluttershy?" Celestia asked.

"Um.. Twilight told us that you told her there was something very bad that attacked Princess Luna and that other Twilight," Fluttershy said.

Celestia nodded. "Yes, we don't know for sure, but evidence seems to indicate it is true."

Fluttershy looked nervously around her. "I've been thinking, Cadence was poisoned, and Star Swirl claimed it was all his fault. But he also said he had lots of involvement with Nightmare Moon. He's... gone now so we can't check, but what if he was corrupted, too? Or just tricked into poisoning Cadence. So if it attacked Cadence, and that other Twilight, it was trying to stop the wedding, wasn't it?"

Celestia winked. "Just between you and me, I thought all that Nightmare Moon talk was just a crush Star Swirl has on my sister." Her expression became serious.  "Unfortunately, if that is true and he was corrupted, that would mean whatever this thing is, whatever it's planning, has been in the works for over a thousand years."

Fluttershy's eyes went wide. "Oh, my..."

Celestia stared wistfully at the happy newlyweds. "Thank you for your insight, Fluttershy. If this thing is trying to stop the wedding, it would seem it has failed, but the day is not yet over. Enjoy the festivities, Fluttershy, but stay alert. I will fetch your Elements of Harmony, just in case."

Celestia turned to leave, hesitated. "Fluttershy, don't tell anypony what you just told me."

Fluttershy frowned. "Um, okay, but not even my friends?"

Celestia shook her head. "No, look how happy Twilight is, let her enjoy this. If something happens, we will deal with it, but if nothing happens, I don't want her getting all freaked out about it. You know how she gets."

Fluttershy giggled. "Yes, very well then, your highness."

Celestia gave Fluttershy a quick hug with her wing. "Thank you, Fluttershy."

* * *

As the hour of the wedding reception approached, Celestia had doubled her security details, reinforced Shining Armor's forcefield, and instructed Luna to keep watch. The party had begun with the traditional cutting of the wedding cake (Celestia had insisted on it coming first), and so far nothing had gone wrong.

Pinkie Pie yelled, "Let's get this party started!" and the DJ, Vinyl Scratch, threw on music Twilight had selected. Twilight took a deep breath and grabbed a microphone with her magic, then dropped it to the ground in shock.

A swirling green portal had opened in the middle of the party. On the other side, Fizzle Hooves channeled her magic and grinned at Trixie. Trixie smirked and looked eagerly into the portal. "Master, glory!"

Fizzle Hooves laughed. "For you, Trixie. Not for me."

Trixie emerged from the portal and her horn began to glow. Celestia fell to her knees, clutching at her head. Her vision blurred, her mind felt like it was on fire, the pain was staggering. All around her, the other ponies suffered the same affliction.

"Princess Celestia, this is the end. Your evil has claimed the lives of many good ponies. No longer," Trixie declared. One of the voices in Trixie's head cooed, Look at my sweet little glutton, mmm...

Celestia grit her teeth. "Wh-what have you done?"

"A bit of treachery, a simple bit of disguise as a scullery maid, and a spell component goes into the wedding cake mix. Undetectable, and nothing more than a seasoning until I cast my spell to activate it. But don't worry, you won't have to think about any of this or that. Your life ends today," Trixie said calmly.

"You p-poisoned the wedding cake? Wh-who are you?" Celestia asked, struggling to remain conscious. She had ate quite a bit of the cake.

Trixie smirked. "My name is Archmage Fizzle Hooves, and I shall have my revenge!"

The three voices erupted into a cacophony of laughter.

Trixie's horn glowed brighter and all around the party everypony fell unconscious. Everypony but one. In Hoc Signo Vinces had not had any of the wedding cake, for she couldn't eat it without removing her helmet and was too ashamed to do so. Winny stared in horror as the robed unicorn sauntered over to the body of Celestia.

Winny shook Star Swirl. "Uncle!"

Trixie slowly drew a sword from her waist and prepared to strike a killing blow. Winny regained her composure and cast one of the spells she had learned from the monks back home - a wall of moonlight. The shimmering tapestry of pearly-white force appeared between Celestia and the attacker. The voices snarled in confusion.

Winny yelled, "No, don't do this!"

Trixie staggered back from the wall of moonlight, then whirled about and smirked at her armored interloper. "Silence, foal. You have no purpose but to die by my hoof."

Winny's horn began to glow once more and a sword-like construct made of moonlight shimmered into existence and struck at Trixie. Trixie parried the moon blade, causing a shower of sparks to bathe her smirking face with a hellish glow.

Slowly, the two unicorns circled until, with a snarl, Trixie brought her sword down in a cleaving arc, then when Winny moved to parry the attack, Trixie feinted and cut low, the blade of her sword cutting a clean line across Winny's foreleg armor. The two slowly circled again.

Trixie was impressed, she did not expect anypony to be putting up a fight tonight. It was a pity she would have to die like the others. Trixie attacked again, much more aggressively. She advanced in a series of lunges, each one met with a loud crack of Winny's moon blade as she desperately parried. Winny was pushed back with every slash, hoping her uncle, or anypony, would soon recover to aid her.

Winny stumbled over a stricken pony. She staggered backwards even farther, Trixie pursued her relentlessly, slashing out at the armored pony with a ferocity that stunned both unicorns. Winny was driven to her knees. She raised her moon blade to block yet another onslaught, only to see her weapon fizzle out of existence as Trixie's horn glowed brighter as she cast dispel magic.

"Enough. I haven't the time for this," Trixie said. Her horn glowed, and Winny's armor began to smoke. Winny screamed and hurriedly discarded the scorching armor.

Trembling, Trixie stood over the exposed Winny, the blade of her magical sword at Winny's throat. She looked into Winny's strange, fiery eyes that pleaded up at her, and recoiled in disgust. For reasons unknown to her, instead of killing this strange unicorn as the voices urged her, Trixie instead growled and bashed Winny with the pommel of her sword then turned and walked back towards Celestia.

The sole audience of this dire duel had been Princess Luna, who flew as fast as she could from the observation tower towards the reception. She paused momentarily, amazed at all the unconscious ponies. She wasn't sure what was going on - there was a strange, yet all too familiar, pony crying on the ground near a heap of melted, golden armor, and a robed pony walking towards her sister with a sword held in her magical grasp.

Winny sobbed, "Luna! Help!"

Luna knew that voice. "Winny?" She stared inquisitively at the daughter of the Unliving Queen. Her mane and tail were a dark blue, just like her mother's had been, but without the streak of color matching the aura of their magic that the Queen, and Twilight Sparkle, possessed. Her pale white coat had an ashen, corpse-like appearance. Her eyes burned with the same unholy fire as her mother's, but these flames lacked the intensity of the Queen's. They were softer, gentler. On her flank, her cutie mark smoldered like a brand with the same unholy fire as her eyes. It was of a dragon eating its own tail, an ancient symbol that represents the cycle of life, death, and rebirth, leading to immortality.

Luna focused back on the robed unicorn - Winny could wait. She channeled her powers and directed a flurry of shooting stars at Trixie. They appeared as streaking moonbeams until they closed in on Trixie, where they became glowing missiles with fiery tails. Trixie dodged and rolled through the barrage of shooting stars, deflected them with her sword, but she was overwhelmed and roared in pain as they exploded around her.

Trixie looked up and snarled. The three voices in her head began to chant, Kill Luna. Kill Luna. Luna must die. Trixie bellowed, "Luna! You must die like the others!"

Luna smirked at the attacker's audacity, then conjured up a massive storm cloud. Lightning bolts coruscated down from the cloud and coursed through Trixie's body, looking for ground. Trixie was at once both confounded and in agony. She had never known Luna held so much power, let alone experienced it herself. The voices urged her to defend herself.

Trixie's horn began to glow and she stood on her back legs, thrusting her front hooves towards the sky. A barrier of force enveloped her and deflected the bolts. Initially, she was successful - the lightning rebounded from her shield, harmlessly striking the grass. Soon, though, the lightning came with such speed and power it coursed over her shield and into her body and she could only shrink from it, convulsed with pain, her knees buckling, her powers at an ebb. The voices chaotically shouted a thousand different spells for Trixie to cast to escape the situation, but she was in no position to perform any more magic.

Luna descended and hovered before Trixie as lightning continued to strike. Winny crawled over to their savior and wrapped herself around Luna's hind leg. Trixie was nearly unconscious beneath the continuing assault of Luna's lightning. Tormented beyond reason, betaken of a weakness that drained her very essence, Trixie hoped for nothing more than to submit to the nothingness toward which she was drifting.

Luna smiled down at the enfeebled unicorn as Winny struggled to her feet besides her hero. Luna nodded at Winny then said to Trixie, "Foal. Thine puerile skills are no match for my power. Thou darest to attack us here? Thou hath paid the price for thine lack of vision. Now, thou shalt pay that price in full."

Trixie looked up at Luna, fear in her eyes. "W-Why d-didn't you eat your c-cake..."

Luna laughed and the outpouring of lightning from the cloud increased in intensity. Their thunder boomed across Canterlot, the brightness of their flashes was blinding. Trixie's body slowed, wilted, finally crumpled under the barrage. She looked lifeless, but her chest still moved as she took in labored breaths. Luna hissed maliciously and the lightning ceased, the storm cloud vanishing.

Luna looked down at Trixie and grinned. "Insidiosus Diabolicus, I presume?"

Winny hugged Luna, tears in her eyes. "Oh my gosh, I thought everypony was going to die."

Luna smiled broadly. "Not on my watch."