During her first years in the throne, Princess Twilight Sparkle began massive renovation projects on Canterlot Castle, as a means to create new job opportunites for newly arriving citizens from outside Equestria, and so she can finally have bookshelves on every wall.

This, of course, involved a complete inspection of all the aging plumbing of the castle. Though some has been fixed before in the past, there were several sections that had been neglected. Though the castle didn't seem to be losing any water pressure, Twilight's neurotic nature felt it necessary to make sure every inch of piping was checked.

Little did the plumber crews know they'd find something as grotesque as what they found deep under the old guard quarters' showers. Even more so was the sickly blue glow of the gem attached to the pony-shaped galvanized enclosure. The glow of an ancient Vitality Gem; somepony was still alive in that terrifying metal coffin, and probably as been for hundreds of years...