Maud Pie has a reputation for being one of the strongest individuals, if not the strongest being, to ever walk the face of Equestria. It was for this very reason that a mysterious band of captors became fascinated to see what it would take to break Maud's seemingly eternal calmness. Not to mention the fact she was the older sister of one of the Elements of Harmony, which was bound to get them a hefty ransom price.
For hours on end after she was captured, Maud was subjected to a number of various torture methods: tickling, earsplitting rock music, hypnosis, and even water drop torture. No matter what her abductors did, Maud's emotionless demeanor never broke.
Becoming fed up with their hostage's lack of fear, anger, or indifference (or any visible sign of emotion), Maud's captors then voted to keep her locked away in a solitary room with the hopes that the isolation would cause her to finally break. To keep her immobilized, Maud was locked inside a thick metal casket forged with some of the strongest metals known throughout Equestria.
Or at least, that's what her captors assumed.
Being the geology expert, Maud quickly deduced that the coffin restraining her was comprised of particularly weak metals she could easily bust her way out of. However, she chose to bide her time like she'd been doing from the moment she was whisked to wherever it was she was being held. She knew each of her abductors' names, as they'd been ignorant enough to use them in front of her. She'd also memorized each of their faces, which would be very useful for her friends in case any of the thugs made a runner.
Before she was left alone, one of her abductors even gagged Maud's lips with a metallic muzzle to keep her from calling for help. Not that it would've made any difference. Once she was certain the coast was clear, Maud would break free of her bindings and dish out some long-awaited comeuppance on her captors.

Of course, that was if Pinkie didn't get to them first.