Started off well enough. Small Goblin ambush managed to pick off a few of my dwarves, but I got most everyone inside. The goblins wanted to go after the easy pickings, intimidated no doubt by the looming presence of the vast tower of doom above my fortress and the blood-and-vomit-covered walls of the fortress' entrance.
But they finally worked up the courage to ascend the spiral staircase into the fortress. The first maceman to the top inadvertently tripped a pressure plate and stumbled right into a row of cage traps. But it was too late, the floors of the spiral staircase had already retracted from beneath his goblin brethren, sending them hurtling to the ground far below. A lucky few had only just begun their ascent and their fall was short and their injuries quite slight.
I knew I had scant moments before they would hurry out of the kill zone. So I made a quick decision to order the use of the doom tower. Never before used, it seemed like a good opportunity to give it a low-risk first test firing. The switch to slam shut the front entrance was thrown. A few goblins managed to make it out safely before the doors slammed shut, but "No matter", I thought. The others won't be so lucky. The firing lever was thrown and in a few seconds, an enormous wall of watery destruction would hurtle down the spiral staircase, smashing the goblins against a wall of spinning saw blades.
But no... alas, I forgot to wire up one of the blast doors. Instead of having the intended effect, I'd accidentally created an over-powered self-destruct button.