Summary: Arthur knew of the distinct shape of a Serket's stinger. He knew that no one who bares the mark of their sting will ever live long enough for it to scar. And that is why he can't take his eyes off the shiny white scar on Merlin's lower back.

Disclaimer: I don't own Merlin, I'm just barrowing the characters for a while.

So far, this has at least three parts, not sure how many it will end up with after that. I want to try to make it slash but for some reason every time I try it never actually turns out that way so we'll see.

Also, this takes place after 4x09 (since that's as far as is out when I wrote it) and has spoilers through that.

.oO***Oo.

The Darkling Woods were a very dangerous place. Arthur knew this and, though he would venture there when necessary, he understood the risks of that forest and tread with utmost caution.

When he had been younger (old enough to know better but too young to care) he and several of his knights had followed a band of bandits into the forest. The bandits inadvertently wandered too close to a serket nest before the patrol caught up to them. Only a few were still alive, writhing on ground and gasping for breath as the final stages of the painful poison ravaged their bodies. They were met with the same injury on each body they checked for life.

A single puncture wound, oval in shape, mostly located on the torso and varying from two to three finger's width across and a finger's width tall. At first the wounds appeared to have smooth edges, but later inspection of a cleaned one would reveal the stingers to have small ridges all the way around. Small veins of black led away from each puncture, the skin dented in slightly as though the flesh beneath had simply disappeared.

There were signs that several bodies had been dragged away. For food, Arthur assumed.

The young prince would have left it at that. These were dangerous creatures, yes, but he didn't have enough men with him to exterminate a nest of (obviously) poisonous creatures and he knew the townspeople knew to stay away. They spoke of these woods in whispered warnings. Only the foolish and the suicidal ventured here.

When a loud hiss filled the clearing, he had briefly wished he'd listened.

The scent of the bodies, fresh kills, had caught the attention of a single youngling. It was still growing so its armored body had several gaps they were able to take advantage of. Later he would truly understand how lucky they were that it was just the one, but as Sir Robert landed the killing blow and as the youngling serket's stinger slipped into the knights flesh it was hard to appreciate.

Sir Leon was with them that day. He was the one who suggested cutting the stinger and taking it with them. (He'd been bitten by a poisonous snake once as a child but his father had been an intelligent man. He was quick to catch the snake that bit his son knowing that the poison itself is often used in the creation of an antidote.)

They rode hard through most of the night, hoping to get Sir Robert and the stinger to Gaius before the knight could fall to the same fate as the bandits, until it became apparent that the knight could travel no more. Sir Leon was sent ahead with the stinger and as a detailed description of the creature as they could manage.

Sir Robert never made it back to Camelot alive.

Arthur was forced to watch each stage of the poison's progression and, in his guilt at leading the man to his death, he committed each one to memory. He watched as Sir Robert shivered, even as his brow burned with fever and sweat dripped from his hair. He watched as all color drained from Sir Robert's skin. He watched as the black veins appeared on Sir Robert's skin. He watched as Sir Robert tried to claw at his own flesh and rid himself of the infection until they were forced to restrain him. He watched as the black tendrils grew and Sir Robert (a man he had seen take a knife wound to the stomach stoically) screamed in agony at the lightest of touches. He watched as Sir Robert begged them to kill him, to end his suffering. And finally, he watched as Sir Robert thanked him with his last breath for doing so.

Later, Gauis would tell him he had done the right thing. That there was no antidote for a serket's poison and even if he had gotten the knight back to the castle, there would have been nothing the physician could do but ease his pain and end his suffering. Arthur had spent every spare moment he had for almost a week reading up on the creatures that had ended his knight's life (his guilt allowed no other alternative).

He came to the conclusion that such a poison was too dangerous to be kept in Camelot and too torturous for the young prince to ever consider using on even his worst enemies. Young Arthur didn't doubt that his father would take full advantage of having access to such a rare poison if he got his hands on it, however. So he ordered the stinger and every drop of poison Gaius had collected from it burned (he was relieved to find out that Gaius had never bothered to collect any).

So yes, Arthur knew of the Serkets and the distinct shape of their stingers.

Just as he knew that no one who bares the mark of their sting will ever live long enough for it to scar.

And that is why, as Merlin pulled his rain-soaked tunic over his head and bent over to lay it out by the fire in the small cave, Arthur couldn't take his eyes off the shiny white scar on Merlin's lower back.

His manservant turned to him, a curious look in his eye but all Arthur can see in his mind is that scar. A ridged oval with dented veins of white flesh that he knew had once been black.

And he realized, in that moment, just how close he had come to losing Merlin without even knowing it. And he wondered, as his eyes flicker over the other scars of all shapes and sizes, just how many other times he had almost lost his closest friend without ever being told.

Merlin's worried, "Arthur?" snapped him out of his reverie and he allowed his worry to turn itself into anger. Because he knows that scar has not always been there (and he'll never admit that he's just a little furious with himself for not noticing when his friend's body had become more scarred than some of his knights).

Arthur's eyes burned with confused anger as they met Merlin's and he quietly whispered, "You should be dead."