Domination of Equestria - T+32 - days.
It was a massive mirror.
At least, that’s what it looked like to the untrained eye.
To the trained eye, the practiced eye, the Evil Eye, it was a massive glass focus.
The focus of terrible magical energies which at a moment’s notice could be brought to bear anywhere in Equestria, along with a large swathe of the countries which made up its borders.
The Solar Eruptor, greatest of the Overlord’s weapons, perched right at the very top of the snowy, icy peak of the Canter Mountain, looming over the capital of Canterlot, gazing balefully across the subjugated land of Equestria, was undergoing its final mounting.
Ponies, changelings and all manner of other creatures swarmed around the small summit camp site, their sense of urgency fed by the imposing presence of their new Overlord himself, there to oversee the final preparation.
“Gulp...My Master, as you can see, we’re undergoing the final mounting now. Once in place we will activate the shielding runes which will draw power from the Solar Furnace below. At that stage, we are fully confident that nopony will be able to so much as touch any of the equipment, let alone damage it.”
The Forepony was wringing his hooves. His concern was understandable, the Overlord had been scowling ever since he had arrived on the frozen peak.
“Tell me Forepony, I don’t see the vents for the Furnace up here.”
“Um...No Master, they come out around half way up the mountain.”
“Half way up?”
“Ah...Yes?”
Was that bad? The Forepony was now very concerned about the Overlord’s scowl. Especially because it now seemed to be directed expressly at him.
“Mr Forepony, what is the range on those shielding runes?”
“Oh...well they’re designed to cover the entirety of the apparatus here on the peak. To prevent undercutting and improve efficiency it’s a close formed, shaped field. It should be around...four centimetres from all of the equipment?”
“How far down do the runes extend?”
“Ssss...well the entire peak…”
“So not the exhaust vents halfway down?”
“Grrr...no?”
“So you’ve left the exhaust port open to attack, is that safe to say?”
“Gulp...it...it...it would seem so, Master?”
Welp, good thing he hadn’t had anything to eat for the last six hours, as per guidelines when dealing with the Overlord. The Forepony was very glad, as he was certain that under that gaze he had utterly lost control of his bowels.
“You’ve left an open exhaust port which leads into the heart of my reactor exposed to enemy aerial attack. I find your lack of foresight disturbing.”
“Mmmmmm...Master, please, we can correct this!”
“Indeed you can. And you will. Split up that exhaust. Run the primary trunking inside the mountain until the halfway point. From there, you will split it into at least fifty smaller outlets no greater than a hoof wide, and scatter them randomly all over the upper reaches of the mountain. Also I want any vertical sections to have switchbacks and dead ends. I don’t want more than three metres of straight piping. Do you understand?”
“Y-y-y-y...Yes master!”
“And for the love of all things unholy get them covered by shielding runes!”
Overlord Rule No:25 No matter how well it would perform, I will never construct any sort of machinery which is completely indestructible except for one small and virtually inaccessible vulnerable spot.