"There you are," said one guard to the other. "The sun's nearly down. Do you even have your sword with you?"
The second guard was looking a bit disheveled - he didn't even have his helmet on - and had arrived, by running, holding an iron shovel. He checked himself, then his backpack. Finding no sword in there, either, he at least put away his shovel. "No sword, but I've at least got my axe. And my bow."
"Give me the axe, then, and I'll give you my sword. I'm a better shot with a bow, anyway." He made sure that he had easy access to the axe, then got out his bow, and checked his arrows, to make sure that he had enough.
They left the gate northward. After peering around the northwest corner, to ensure that everything was clear, they doubled back southward, passing the gate on the way to the southwest corner. It was on their way back to the gate that they saw a giant spider as it attempted to scale the walls. Since they had the jump on it, they closed in and took it in melee. It was finished with a blow from the iron axe, but it was worn, and the head came loose from the handle in the process.
Frustrated, the first guard took back his sword, and they returned to the gate for the next portion of the watch.
"You stay here, while I go get your sword and helmet. I'll run your shovel back, too."
The other guard handed over his shovel.
"If any other monsters appear and are close enough, shoot them."
He waited by the gate, wondering what might come out tonight. The giant spiders were the worst, it seemed, since they appeared in numbers and could scale the walls. As he contemplated this, though, he noted that one of the tall trees in the nearby wood seemed darker than the others. He looked upon it, and was overcome by the ominous sound that seemed to come from everywhere at once. The tall, dark creature turned to face him, and their eyes locked. Carefully, he drew his bow.
"DON'T SHOOT IT!" he heard, but the cry came too late, and he had already released the arrow. Just as it seemed likely to hit, though, the creature disappeared.
"Where'd it--" but he was swiftly stricken from behind.
Before anyone knew what was happening, they were all fighting for their lives, as the enderman teleported around, leaving death piles and missing blocks in its wake.