Severus had been walking back from the greenhouses just after dusk when he noticed a rather strange party heading towards the Forbidden Forest. Filch led the group of students, including Potter, Granger, Longbottom, and Malfoy. Severus had no doubt that it must be their detention; he had signed Malfoy off to McGonagall just that morning. But he had no idea that they were going to forest.
He looked to Lily, who was walking just behind him to ask what they were going to do. But she wasn't looking at him, nor Potter. She was staring at the dark tree line with fear in her eyes. Severus could not remember anything of note that happened in the forest on the night of Potter's detention. Malfoy had complained loudly about it to him the next day, but he hadn't thought too much on it.
He continued to watch the group as they neared Hagrid's hut. The half-giant greeted them with his massive dog and led them into the forest. A highly unusual activity for detentions. Severus suddenly wondered if Dumbledore had his hand in this somehow.
Lily was standing behind him now. "Follow them, Severus."
It was strange for her to give such a direct order and he wondered why she was so fearful. Naturally, the forest was full of dangerous creatures, but not many of them lingered near the school grounds. And, as much as Severus disliked the man, Hagrid was probably the most knowledgeable and capable person to have in the forest.
"What is it?" he whispered to Lily.
Her hand was suddenly on his sleeve, though he could not feel it. "Just follow them, Severus, and be careful."
He frowned and shoved the dried Valerian Sprigs, which he had just acquired from Pamona Sprout, into an inner pocket. With the sun already set, he had no need to conceal himself in the darkness. He took a direct route to the forest, a couple of dozen meters away from the detention group.
He did not take out his wand for a light, but carefully made his way towards the group. It was less than a minute that he saw their lamplight blinking between the trees. They seemed to have split into two groups. Potter and Granger were with Hagrid. Then Malfoy must be with Longbottom. Severus frowned, wondering the wisdom of letting two first years students wander the forest alone.
He kept a distance and could not hear their whispered words, though it seemed they were looking for something. Severus stayed in the shadows.
He could easily see Lily, her body unnaturally lit. Still, she was not looking to Potter, but at the shadows surrounding them. He was ready to question her again, when Hagrid started shouting in alarm. He looked back to the group and saw the children had crowded near him as he pointed his crossbow into the trees.
"Who's there? Show yerself — I'm armed!"
The shadows rustled and Severus found himself crouching, ready for an attack. But a centaur walked into the clearing. Severus knew there was a sizable herd of centaurs in the forest, but he had never seen one himself. Hagrid recognized him.
"Oh, it's you, Ronan. How are yeh?"
The centaur was aloof and maintained a casual conversation with the group. With Hagrid speaking at a normal tone, Severus could now hear that they were searching for something that was killing unicorns. Severus had never heard of anything hunting unicorn. For his potions, unicorn hair was highly valuable as it could only be given, not taken from a unicorn. And the creatures tended to only want virginal women around them to pluck the hairs.
The centaur, soon followed by another, was unhelpful. The group eventually moved away and Severus with them. He kept an eye on the centaurs for a moment, knowing the creatures could easily detect him. But they gave no sign of noticing him and soon they wandered out of sight.
Hagrid, Potter, and Granger were back to whispering in low voices. Though Severus noticed Potter kept looking over his shoulder. He didn't know if the boy could sense him, or was simply looking out for more centaurs.
There was a sudden splash of color as red sparks were sent over the tree line. Hagrid left the students to investigate and Lily's hand was on his sleeve gain. "Severus this way, quickly. This way." She motioned him away from the group.
"What is it, Lily?" he hissed as the light from Potter and Granger disappeared between the trees.
"He's here, Severus. You have to find him and stop him before he discovers them."
Severus felt a sudden numbness in his limbs. "Who, Lily? Who is here?"
She wouldn't look at him and was almost running between the trees. He reached out and found his hand sliding through her arm. Lily didn't turn around, she fled into the trees and Severus found himself slowing, watching her ethereal form disappearing between the trees.
He had the sudden thought that perhaps she wasn't running towards something, but away. He stopped completely, trying to gather his thoughts. He looked up, past the tree line. It was a clear night, but the moon had yet to rise. Severus circled slowly, gathering himself. The darkness of the forest was almost…comforting. He had spent so much of the past years in dark corners. While he had to come into the light to play his double agent role, it was in shadows he could disappear.
Footsteps, slow and unnatural. Severus melted between the trees, trying to distinguish the direction. It was nearby. More footsteps, but more…legs? Severus barely had the thought before a snow white creature appeared nearby. Severus edged closer and crouched at the brim of a small clearing.
It was a unicorn, a young male by the size and shape of the horn. It paused and one eye peered at Severus. Then it moved past him and the creature stepped forward, limping badly. The left flank was severely wounded, like a slash from some beast. The unicorn knew he was there, it also knew something far more dangerous was also there.
The silver blood shimmered, dripping down the leg and on the grass. The unicorn paused slightly, the head swinging around. His breath was heavy and pained. He jumped slightly, as if trying to encourage his bloodied body to continue moving forward. Then the unicorn knelt, sinking to the forest floor, gasping and grunting.
Something moved from the shadows, and thought it stood in the clearing, it seemed to not have a shape. Like a crouching man, but more like a snake posing to strike. Severus found his fingers digging into the roots near him and his mind automatically clearing of all thought and emotion. It had been some time since he was in the presence of the Dark Lord.
Of course, this Dark Lord was not the power Severus remembered. He was weak now, more inhuman, though it was hard to remember the Dark Lord ever being human.
He began to drink the blood and Severus felt sick. He knew he should leave, run away. Just as Lily had. His body wouldn't move and all he could do was watch and listen.
A small light appeared in the distance. The Dark Lord paused, then vanished back into the trees, like a frightened deer. The strange sight alarmed Severus, but he felt blood coming back into his legs. He stood up slowly, eyes draw to the nearing light. A lantern, undoubtedly. But was it Hagrid? The students? Or someone else?
"Look —" A murmur and Potter stepped into the clearing.
Malfoy and Hagrid's dog followed. The small group stood transfixed at the sight of the fallen unicorn. The boys stayed at the edge of the clearing, obviously alarmed.
"Run." Severus turned quickly, and found Lily behind him. Her eyes were dark and her form was somehow…more translucent. "Run, Harry. He's found us."
Severus whirled around just as the hooded figure emerged from the trees, just across the clearing from the boys. Severus was already moving as Malfoy screamed and fled back into the trees, quickly followed by Hagrid's dog. Potter fell to his knees, clutching his forehead. His scar, Severus realized, as he dashed across the clearing.
The Dark Lord was crouched over the unicorn, emitting a strange guttural moan. As if it couldn't speak or breathe, as if his throat had been slit. Severus quickly reached Potter and whirled around, his wand drawn and his stance ready for battle.
But no hooded figure lay over the unicorn anymore. The white creature seemed suddenly brighter in the dark clearing and Severus searched the trees, but found no movement. The Dark Lord had fled. Severus crouched down next to the boy. "Potter? Potter, are you okay?"
The boy moaned, hunched over and still clutching his forehead.
"Potter, we need to leave. Can you stand?" Severus almost reached out to shake the boy, but heard movement behind him.
Back to his feet, Severus found himself facing a centaur. Not one of the ones that Hagrid had spoken with earlier. "Potter? Is that Harry Potter?"
Severus recognized him as Firenze. Though it seemed like a very long time ago that the centaur had come to Hogwarts as a Professor. Severus had never personally spoken with him, having very little interest in Divination. "Did you see what happened?"
The centaur stared at him, his blue eyes shimmering. "We need to get the boy out of the forest. It isn't safe."
"It's never safe." Lily spoke from behind Severus and it took all of his self control to not flinch. Instead he turned around calmly and saw that she was kneeling next to Potter. Her legs were so translucent that she seemed to be sinking into the earth. He wished he could speak with her, but he didn't dare with the centaur there.
He knelt down and forcibly picked the boy up by his shoulders. Potter seemed to be regaining himself and was able to stand unaided. His eyes were wide and panicked, his skin as pale as Lily's. "What was that?"
Severus carefully looked over the boy, but he seemed unharmed. "Can you walk?"
Potter looked confused and stared passed Severus' shoulder to the centaur standing nearby. "What?"
Firenze stepped forward. "You need to leave, Harry Potter. The forest is not safe for you."
"Not safe," Lily echoed and Severus closed his eyes, trying to concentrate.
"Hagrid," he murmured. "Where is Hagrid?"
Potter gained a little more focus. "Red sparks!"
"What?" Severus asked, but the boy had already raised his wand and let loose a small jet of red sparks.
Potter gave a shaky sigh. "He'll come now. So did you see what happened?" He shifted so he could look at the fallen unicorn. "That was aweful." He rubbed his forehead at the memory and Severus found himself taking Potter's wrist to still the action. The boy stared at him, but didn't pull away.
Firenze spoke, soft and deep, "Harry Potter, do you know what unicorn blood is used for?"
Potter shook his head and Severus didn't answer. Firenze stared at him for a long moment and Severus found himself clenching Potter's wrist. The boy flinched and he loosened his grip. Potter let his arm fall to his side.
"It is a monstrous thing, to slay a unicorn. Only one who has nothing to lose, and everything to gain, would commit such a crime. The blood of the unicorn will keep you alive, even if you are an inch from death, but at a terrible price. You have slain something pure and defenseless to save yourself, you will have but a half-life, a cursed life, from the moment the blood touches your lips."
"But who'd be that desperate?" Potter asked. "If you are going to be cursed forever, death's better, isn't it?"
"Is it?" Lily moaned.
The centaur was standing next to Potter now, leaning forward and almost whispering. "Unless all you need is to stay alive long enough to drink something else —"
"Harry?" It was Hagrid and the other students, including Malfoy. "Firenze? Professor Snape?" He sounded most confused at the end. "What is it? What happened?"
Firenze stood straight. "Hagrid."
The half-giant looked momentarily confused, but then noticed the unicorn. He immediately went to it's side. "Shame," he murmured. "Poor thing."
Granger stood next to Potter, putting a hand on his shoulder. "Are you hurt? Why did you send up red sparks?"
Severus noticed he was shaking slightly. Potter's voice was quiet. "I'm fine. I think I saw…something. I think it was the thing who killed the unicorn."
Granger gasped. "What was it?"
The boy shrugged and looked to the ground, exactly where Lily was still kneeling. "Dunno. It looked kind of like a person, but wrong somehow." He glanced up at Severus. "Professor Snape came running and…I don't know what happened."
Granger's fingers were clenching the robes on his shoulder. "Are you sure you're alright?" She looked up to Severus. "What was it?"
He was saved from answering as Hagrid returned to the group. "We need to get going. Whatever was here can't be far."
Firenze nodded. "Then I will leave." He stared at Potter for a moment, before his eyes flickered to Severus. "Good luck." He trotted back into the trees.
As Hagrid tried to usher the students back to the trail, Malfoy stepped next to Severus. "Professor? What are you doing out here? Well, I hope you report this. My father would be furious to know what they are making us do!"
Severus put a hand on Malfoy's shoulder and turned him so they could begin walking out of the forest. "I agree with the high irregularity of this detention. Be assured, Mister Malfoy, I will submit a complaint to the headmaster." Hagrid tensed at his words, but was too distracted with watching the trees for danger to reply.
Malfoy smirked and stepped forward. He seemed to find safety next to Hagrid's giant, slobbering dog. Severus was at the edge of the group and took a moment to look back at the clearing. Lily was standing next to the fallen unicorn now.
"Poor thing," she muttered, over and over.