Forethought

"Put the magnagorgon over there. Good. What is it?"
The acolyte wrung his sweaty hands and spoke. "Great one, you have captured by your incomparable arts some of the most dangerous creatures. The magnagorgon, the tyrannolisk, the mindful mass . . ."
"Yes, yes."
"In furtherance of what aim are you having us haul them to this empty field? Not that we mind, of course, but . . ."
"An empty field. You do not see, as I do, the complex I will erect here once all my sentinels have been placed."
"Ah!"
"You see now? When robbers intrude and run across these monsters, they will wonder how such colossal beasts could be there, being bigger than the corridors and doors as they are. These magical mirrors I have devised will capture their expressions at that exact moment. Oh, how we will laugh!"
"Ha ha ha!"
"A ha ha ha!"
"Gya ha ha ha ha!"

"And that's probably how that magnagorgon got in there."
"I can't see any other explanation, frankly."
Finis