Having subjugated the former Princess Luna, (now known as Wet Dream,) Empress Cadence finally has enough magic to go after Celestia. But The sun princess is stronger than her sister. If she fights back, she might be able to hold on to her mind and her magic, or at least some of it, until the spell runs it's course. And Cadence cannot let that happen at all costs.

So when Celestia is ambushed and struck with Cadence's curse, it's been modified a bit. Sure enough, Celestia starts fighting back as soon as the initial shock of magic striking her horn wears off. But as she, like her sister before her, floats into the air, something starts happening to her wings. The spell strips her of the pegasus part of her alicorn magic, leaving her greatly weakened, and her feathers begin to fall out as her huge wings shrink and wither away.

The muddled confusion of seeing her feathers falling out is enough to break her feeble resistance, and the magic overwhelms her mind as well. Her train of thought spirals off into pink, bubbly nonsense, and her once considerable intelligence leaks out of her brain and begins padding out the "Royal assets" which have sprouted on her chest. By the time her rainbow hair has faded to a pink and blond color, the former princess is unrecognizable.

And with the alicorn's out of the way, Empress Cadence can focus on other targets. Something will need to be done about the elements of harmony after all.

Part one >>3325697

Part two >>3325698

A quick thought. Since I guess Im doing enough of these to think about a timeline, this happens sometime between season 2 and 3. Twilight is still a unicorn, and Discord is trapped in stone. Though if Cadence causes enough chaos, that last bit might change. And, well. Cadence does have a bunch of alicorn-pegusus magic on hoof now. Maybe her next servant can have a nice pair of wings.