Applejack and Applebloom didn't know who had captured them or why they awoke bound together in the strange padded cavity, but they quickly come to realize that their world would be focused down onto their bound and exposed feet.
The laser sweeps up and down their soles and toes at an absolutely agonizing pace. It took 5 minutes to move from the tips of Applejacks toes to the end of her heel.
It felt intense. Like the sensation of Rarity's manicured nails skittering endlessly upon every inch the laser pressed itself against. And as the hours passed the sensations only seemed to heighten more and more!
Whoever had captured them was hell bent on rewriting the sensitivity of their helpless but durable earth pony soles.
And inside the prison all AJ and Bloom could do is squeal, giggle, and beg for a mercy that didn't seem to come.