Once Upon A Time: The Ice Castle.

The main gatehouse of Harlech Castle. The step...
The main gatehouse of Harlech Castle. The steps were originally a drawbridge. As well as this formidably defended entrance, the castle also had a fortified dock so that it could be supplied by sea. (Photo credit: Wikipedia)

Once upon a time there was an ice castle. It had great slabs of ice, within which there were trapped predators from another age, cut from the ice mountains and dragged to the castle to put fear into any who would invade.
The castle sat at the edge of the great Norse wastes, so the blocks never melted. If the sun shone its fiercest, the top layer of the blocks would become moist, freezing all the harder with the frost of night. A town had grown up around the castle, and the villagers of the castle were trained from birth to defend the castle with their lives. The castle was not just a defensive building, it was a sacred space.
In part because of the dedication of the villagers, the castle had never been taken. It had exchanged hands from inheritance, and from all the political and royal intrigues. But it had never been taken in an armed combat.
Now, as the villagers awoke, they knew that the world’s greatest emperor was sending his greatest army against the ice castle. It made no sense politically, because the castle did not defend rich lands beyond. The wastes around the castle were barely able to support the few villages that scraped their living from the soil. But it was something that the emperor wanted to do to prove he was better than any of the other emperors who had come before. He would be the one who destroyed the ice castle.
So the great army approached the ice castle. For an army of this size, great supply chains were necessary, bringing up carts of meat, wood, and grain from areas far distant. To feed an army this size was an undertaking in its own right. The emperor, even in his greatness, could not afford to siege the castle. He must take it by force, and quickly, or exhaust his finances and his military power.
To do what none had done before, the emperor had assembled great military engineers. They had no maps of the inside of the castle, because none of the villagers could be bribed and died before they told the secrets. But they had many maps of the outside and felt confident that it was possible to break. The ice could be shattered by sufficient power, but the power had to be concentrated in a single part of the wall.
A great ram was built, long enough that fifty men were necessary to move it. To move the ram, they built a great cart and covered it over with a roof to protect the men. It was this great military machine, pulled by dozens of oxen, that the villagers beheld below them. It was as yet far off on the plain, but coming slowly across the plain.
The villagers met together. They were prepared for fire, for many had tried that. There were great stores of water within the castle, and they could put out fires of any kind. But never had they faced such a weapon. At length, they came up with a desperate plan.
In ones and twos, the defenders of the castle left the castle. Within any great force, there are many who do not know each other. A great army is made up of many packs of men. So few notice when a man here and there goes missing. They think he must have gone off with another group. In this way the defenders of the castle became part of the attacking army. Their success was such that when it came time to man the great ram, with its metal spike for piercing the castle, fully half of the men were those from the defending side. The labor of the ram was heavy and unrelenting, so all the defenders had to do was not protest as much as their fellows to be chosen.
As the ram swung back and forth, half of the men heaved backward even as the other half was heaving forward. After a day of battering, the wall barely had a scratch.
The emperor was upset, and called his engineers. They reassured him and went out to inspect the ram. They failed to inspect the men running the ram and could only show the emperor the calculations that showed the castle should crumble.
For twelve days and nights the ram swung. On every shift the defenders made up half of the crew. And for twelve days and nights nothing happened. At the end of twelve days the emperor abandoned the ram and left in disgust. He left the engineers’ heads on pikes, and moved his armies off to more fruitful lands. Over time the villagers cut the ram into pieces and used it for firewood and to repair their homes.