"Cadance can induce addiction in others. Her size is dependent on how many subjects adore her. Arcane addiction is infectious."

Celestia didn’t know what she’d been expecting when she’d opened the guest room door. Something sane, perhaps - like Cadance and Shining Armor lounging on the sofa, perhaps reading a book, or chatting, or even napping. They’d come a long way from the Crystal Empire, after all.

What she certainly hadn’t expected, though, was a veritable orgy of ponies spread throughout the room, nor Twilight Sparkle joining in. Celestia blinked, spotting Cadance lounging on the bed. Did Cadance suddenly look a bit larger, or was it her?

“Auntie!” Cadance said happily, springing up from the bed. Each other pony in the room looked up at her - quite literally, even in the stallions’ cases. Cadance had grown a good foot and a half, Celestia realized, until she was within inches of Celestia’s own height. She’d known that alicorns grew over time, but this was just ridiculous.

“Cadance,” Celestia said warily. “What’s going on here, exactly?”

Cadance waved a hoof and all of the other ponies - was that Luna’s butler over in the corner, and one of the Wonderbolts on the bed with Twilight? - went back to their fornication. “Just a bit of a party, auntie,” Cadance said, sauntering up to Celestia. An obviously lovestruck Shining Armor tailed her, along with an entourage of several other ponies so close that they nearly had to dodge Cadance’s oversized hooves. “I invited them.”

“As much as I appreciate the pursuit of pleasure of all kinds,” Celestia observed mildly, “I’m afraid I can’t really condone an orgy taking place in the guest suite of the castle. I’ll need you to - “

“Do not question our mistress!” Shining Armor barked. Beside his now much-larger wife, he looked positively like a puppy dog. Then again, the fanatic look in his eyes looked entirely too doglike for Celestia’s comfort. “She is the one above all of us!”

Celestia frowned down at him. Now, that was certainly out of character. “About that, dear,” she began. “Could you possibly enlighten me as to the reason of your apparent growth spurt?” It’s a bit disconcerting, she silently added, as Cadance smiled and looked her evenly in the eyes.

“Oh, it’s just a side effect,” she said. “Come here, Fleetfoot.”

Celestia watched as a light blue pegasus broke away from what looked to be a fivesome and slowly, bowleggedly, wobbled over to the three of them. “Yes, mistress?”

“You love me,” Cadance murmured. She leaned over, brushing her lips softly against Fleetfoot’s mane. “Don’t you?”

“Oh, yes, mistress!”

“How much!”

“With all of my heart!” Celestia could tell that Fleetfoot was about to start babbling. “More than I’ve ever loved anyone!” A chorus of voices popped up around her, each proclaiming their love and devotion to Cadance louder than the last.

Celestia watched - now more than somewhat unsteady - as Cadance moaned, her eyes fluttering and her back arching. She could actually hear the creaking of bone and muscle as Cadance started to grow, a light pink aura around her body flickering with each word of her devotees.

When Cadance finally opened her eyes, she was looking down at Celestia, her long elegant neck actually bending forward to peer down at her smaller aunt. “Mm,” she said, licking her lips. “That felt even better than the last one. I wonder how large I am now, auntie. Seven feet, perhaps?”

“Cadance,” Celestia said. She took a step backward, a glow of yellow flickering up around her horn. “I don’t know what’s going on here, but I’m going to get Luna and - “

“No,” Cadance said simply. Her louder, richer voice rang throughout the room and suddenly every face was looking at Celestia. The smile spread even further across Cadance’s face. “You’re going to stay here. With us.”

Before she could say a word, Celestia had been covered in a pile of pleading, worshipping ponies. “Worship the mistress,” they told her. “Love the mistress. Serve her. Adore her.”

And even as Celestia struggled to resist, she could feel a deep surge of adoration for Cadance in her mind, soon growing into an obsession and a deep, deep need to love her as much as she could. The last thing she saw before going fully under was Cadance, her niece moaning and holding a much smaller Shining to her crotch as she grew and grew and grew, her body growing taller and longer until her horn was nearly scratching the roof -

And then Celestia knew in soul that she loved Princess - no, Mistress - Cadance with all of her heart.