As he climbed the steps leading to the castle's main entrance, Severus cursed himself. If only he had known, if only he had had more foresight, he would have hauled Bellatrix over his head and into the school. If Voldemort intended to hide or do anything else, she surely knew. He had her there, right in front of him, defenceless, and he had let her go. How could he let her go?
The only consolation was that no one but that woman knew of their encounter in the heart of the Forbidden Forest, so no one but himself could blame him.
As he took the first step out of the castle's entrance, he suddenly realised how much time must have passed since his narrowly avoided departure. The sun had begun to rise over the treetops of the forest, and a few brave birds had begun to chirp, oblivious to the battle raging beneath their nests. A ray of the rising sun fell upon Severus' face.
He had always loathed the sun. Over time he had made it his personal mission to avoid it for as long as possible, and for years he had succeeded.
Now, however, as that cone of warm light forced him to squint, he thought it was nothing less than a miracle that he was still able to do something like walk under the sun and be annoyed by it.
Suddenly, as he observed the many bodies lying lifeless on the fresh grass, a new awareness forced him to pause. Severus did not want to die. He couldn't remember how long it had been since such a thought had crossed his mind.
"Professor!"
Hermione's voice woke him.
He turned to see her, Ron and Harry casting Shield Charms on a hooded stocky woman with long blonde hair whom Severus did not recognise. He drew his wand and cast a Stupefy on her, knocking her out instantly. The three students watched as he approached the unconscious Death Eater. He studied her carefully.
"I've never seen her before. She must be new," he said.
He turned to meet the tense faces of the three.
"We need someone important. Someone close to him. Someone like Dolohov or Rosier or Nott."
"The Carrows?" asked Ron as he helped a girl with a bleeding arm back into the castle. "I think I saw them here."
"No," he replied. "They're dead."
"How do you—" Ron started to ask.
"Because I killed them," he replied coldly.
Ron looked at him, half impressed, half intimidated.
"Bellatrix?" asked Hermione, dodging a curse.
It had bounced off a nearby Shield Charm and crashed into the school wall behind her, which crumbled and hit Professor Flitwick on the head.
"Bellatrix isn't here, and I don't think she'll be back any time soon," he said in such a categorical tone that none of them pressed the matter.
"Yaxley?" suggested Harry.
Severus turned to see the boy pointing to a spot on the other side of the park.
Corban Yaxley was fighting a tall boy with long red hair and a large scar on his face. He considered the option. Voldemort had trusted Yaxley enough to entrust him with the task of keeping the Minister of Magic under the Imperius Curse. He wasn't his favourite. He had always found him too diplomatic, too interested in keeping up appearances. But if his intention was to vanish into thin air, perhaps the most cautious Death Eater in his ranks was the one he would involve first.
"You may proceed," he replied.
All four moved towards him at once. They reached Bill Weasley and stood at his side to fight the Death Eater; he turned, confused, first to Severus, then to his brother.
"What's going on?" he asked urgently.
"Not now, Bill."
Bill frowned. His younger brother had never spoken to him like that.
The five of them surrounded Yaxley, who hesitated for a moment, unsure which target to strike. Bill seized the moment and cast a deadly-looking spell at Yaxley.
"No!" shouted Severus, stepping between them and blocking it.
Bill pointed his wand at him, ready to cast one in his direction as well, but Harry stepped in front of him.
"No, Bill, stop!"
Bill, stunned, looked at each of the people in front of him one by one, while Yaxley, even more confused, tried to slip between two boys, but Hermione managed to disarm him in time.
His wand flew over their heads and landed in the hands of Omegas, who seemed to have fully recovered and was walking briskly across the park. She twirled the wand in her hand, smiled at Yaxley and said, "Thank you!"
Then she turned and began to fight a nearby Death Eater, quickly casting spells with both wands.
Severus turned to Yaxley and, with a quick flick of his wand, bound his hands. He struggled angrily, trying to free himself, but to no avail.
"Take him inside," he commanded.
Harry, Ron and Hermione positioned themselves behind the Death Eater and pointed all three wands at him.
"Walk," Ron ordered in a tone of disgust, as if the idea of touching something so vile, even with the tip of his wand, made him sick.
Yaxley took a few uncertain steps towards the entrance to Hogwarts, under the watchful eyes of his captors.
Suddenly, a loud buzzing above their heads forced them to look up. The Death Eaters had taken flight—all of them, in unison. They were riding what Severus recognised as the school's spare brooms, and they were flying higher and higher.
"Are they retreating?" Hermione asked incredulously.
Harry watched them in confusion. "I think they—"
He didn't have time to finish the sentence as another Death Eater, whom Severus didn't recognise, had taken advantage of the general commotion, lowered his altitude and grabbed Yaxley by the hood, dragging him onto his broom.
All four of them immediately ran towards the Death Eaters, but they quickly gained altitude and were soon out of reach. Severus was about to take flight when something whizzed past his head, almost grazing his neck, and sped towards the fugitives.
It was Omegas.
Severus turned to see Stan Shunpike on the ground: she must have knocked him off his broom as he tried to fly and stolen it. When he looked up again, the two broomsticks were almost at the Astronomy Tower.
Omegas cast spells with both wands at the two Death Eaters, who clung to each other as they continued to climb in a desperate attempt to escape. She risks causing them to fall, he thought, and finally took flight.
Flying was difficult. Severus considered it the only skill he had acquired during his career as a Death Eater of which he could be proud. However, he couldn't use his wand or communicate while in the air. The best thing to do, he thought quickly, was to throw himself onto the broom with Yaxley on it, regain proper form, knock out the other Death Eater and bring Yaxley to the ground.
What he hadn't considered was that the Death Eaters knew exactly what he looked like when he was flying, while the woman on the broom in front of him had no idea.
Seeing the eerie black shadow that resembled a large bat flying beside her, Omegas was so frightened that she almost fell off her broom. She clung to the wooden handle with her legs, upside down, her long curls falling over her face.
The unknown Death Eater raised his wand to strike, but Severus reached him in time, returned to his human form and threw him from the broom with a yank. He screamed desperately as he fell from above the Astronomy Tower, attracting the attention of several other Death Eaters who immediately began flying in their direction.
Omegas, who had managed to pull herself together, stared wide-eyed at Severus.
"You can fly?" she asked, clearly impressed.
"Yes," he replied. "I need to get this one down," he said, holding Yaxley by the hood.
Omegas nodded. "I'll cover you."
Severus dived down, clutching the broomstick tightly, while the other struggled ahead of him.
Meanwhile, the woman flew behind them, occasionally turning to cast a spell at their pursuers. Severus turned. Six or seven Death Eaters on broomsticks were hurling curses at her. She darted here and there, dodging them and making sure they didn't reach the broom he was riding.
Severus glanced at the park, which was close by now. It wasn't a good idea to land with seven Death Eaters on their tail and one on a broomstick, just waiting for the right moment to strike. Omegas must have had the same thought, for she suddenly stopped in mid-air, sat upright on the broomstick and began to cast quick spells with both wands, preventing the Death Eaters from advancing.
Severus sped up and reached the ground in less than a minute. Harry, Ron and Hermione were waiting for him at the castle gates. He dismounted the broom, still holding Yaxley by the hood, and forced him to do the same. He handed him to the students, who pointed their wands at him menacingly.
All five of them looked up to see Omegas relentlessly casting spells at the Death Eaters. Someone, Severus noted, had given up and turned back, for there were now only four in front of her, continuing to raise their shields to defend themselves from the barrage of attacks.
Instead of descending, she had begun to climb, pushing them away from the castle. She was past the Astronomy Tower when two more Death Eaters gave up, turned their broomsticks and disappeared beyond the castle. The remaining two continued to fight for a few minutes as the Hogwarts park filled with onlookers.
Finally, the last two gave up. Victory cheers rose from below as Omegas' spell faded and she prepared to descend.
At the exact moment she turned the broom, probably driven by an irrepressible thirst for revenge, one of the two retreating Death Eaters cast a final, quick spell at her before disappearing beyond the castle. She didn't see it, and it struck the handle of her broom, breaking it cleanly, knocking her off her feet and causing her to fall.
Severus heard a series of gasps as everyone present held their breath. He heard Harry shout, "Accio Broom!" but every broom in the castle had been summoned by the Death Eaters and had flown away with them.
He did not hesitate a moment longer; he took to the air, reached the woman halfway and enveloped her. He was not exactly corporeal when he flew, but he could at least slow her fall. He pulled with all his might, and her descent slowed more and more.
When Omegas landed with a thud, Severus immediately returned to normal and stood beside her as a curious crowd gathered around them.
The woman did not appear to have a scratch on her, except she ran a hand over her thick black hair, which came out covered in blood. She smiled, looked at him and swayed slightly from side to side, dazed.
"That was… amazing!" she whispered excitedly; then she fainted.
A low murmur spread through the crowd around them. Severus rose, still standing over the unconscious woman at his feet.
"Someone take her inside," he said brusquely.
Immediately, a couple of boys took her in their arms and escorted her back to the dungeons.
Professor McGonagall rushed out of the castle entrance, breathless and her hat askew.
"What happened?" she asked, a little out of breath.
"They retreated," replied Harry.
He had never stopped watching the sky, as if he expected to see a squad of Death Eaters returning in close formation.
"What?" she said incredulously. "Why?"
The boy shook his head.
Severus, who had also kept his eyes to the sky the whole time, turned to check that Yaxley was still tied up and under guard.
Ron and Hermione had their wands pointed at him, while he, now seemingly determined to maintain a stoic air, kept his eyes fixed on him.
Severus approached cautiously, returning the icy stare.
"He'll tell us," he said in a dangerous whisper.
"Will I?" he replied defiantly.
"You will."
He looked at Ron and Hermione, then nodded towards the castle doors. The two escorted Yaxley into the main entrance and disappeared down the corridor.
"What do we do, Professor?" Harry asked after a moment.
Severus turned to him, puzzled. Not because he didn't have an answer, but because he didn't expect to be giving orders, or anyone willing to follow them.
Harry must have sensed it, because he added reverently, "You're the Headmaster."
Severus looked at him, genuinely surprised. Then he glanced at Professor McGonagall, who also seemed to be waiting for instructions. He considered.
"I'm not," he finally said, nodding to the other professor.
She was stunned for a moment, then smiled at him.
"Very well," she said with newfound authority. Turning to the crowd that still surrounded them, she spread her arms and said loudly, "Go inside and rest. Take care of our wounded and get your strength back. The enemy may be in retreat from this battle, but there is still a war at hand. Be prepared."
All the men and women still in the park moved in unison towards the great broken door of the castle. Someone who passed Severus looked at him suspiciously. Fred Weasley whispered in his twin's ear; Professor Flitwick was careful not to look at him; while Professor Slughorn gave him a curious look, then quickly turned to nearby Professor Sinistra and began to chat animatedly.
Severus, however, was used to this kind of attention and remained impassive, still in the centre of the park, looking up.
"They'll be back, won't they, sir?" Harry asked after another moment of silent staring at the sky. "They won't let us hold one of their own hostage. Not someone that important."
"No," Severus confirmed. "As soon as Voldemort finds out we have Yaxley, he'll send them back."
"What do we do?" the boy asked urgently.
Severus, who had been searching for a solution to the problem for quite some time, suddenly had an idea. He didn't know if it would work, but he thought it was worth a try.
He lowered his eyes to the boy and forced himself to use a tone that sounded calm.
"You're dead."
Harry looked down at his body, as if to make sure he wasn't a ghost.
"No, sir."
Severus rolled his eyes. "Not at this moment, Potter," he said, completely abandoning the composure he had tried to impose on himself. "Earlier, in the Forbidden Forest. You died."
"Oh," he replied softly. "Yes."
"Why did you do it?"
The boy, confused, looked at Professor McGonagall, who shook her head, equally puzzled.
"You know why I did it, sir."
"Yes, I do," snapped Severus, on the verge of losing his patience. "But what made you do it? Was it to save your friends? To save the people you love?"
Harry lowered his eyes, seeming a little embarrassed at the idea of answering the question. Then he raised his head resolutely and met the Professor's eyes.
"Yes."
"You sacrificed yourself for them," he said. This time it wasn't a question.
The boy nodded weakly.
"Good. Out with your wand, Potter."
Harry, increasingly confused but with newfound determination, gripped his wand tightly and awaited instructions.
"Close your eyes," the Professor said firmly, "and concentrate on that feeling."
"Alright," he nodded.
"Raise your wand."
The boy raised his arm and pointed his wand in front of him; only, Severus realised, it wasn't his wand at all. It was Draco's wand. Puzzled, he made a mental note to ask him about it later.
"Higher," he commanded.
Harry stretched his arm until he was pointing the wand at the sky.
"Good," he said. "Now don't lose focus and say 'Enagisium'."
"Enagisium," he repeated.
Nothing happened.
"Concentrate, Potter," he growled.
The boy adjusted his stance and stood silently for a few seconds. Then he tightened his grip on the wand, raised it even higher and repeated in a firm tone, "Enagisium!"
Professor McGonagall gasped and Harry opened his eyes.
All three of them looked up as a huge golden dome expanded and stretched over the castle, the Black Lake and beyond the Forbidden Forest. Severus gave a satisfied smirk, as if he had produced it himself.
"What is it?" Harry asked, still looking up.
"The most powerful Defence Charm in the world," Professor McGonagall said, impressed. "There are very few documented cases of an Enagisis Charm[1] working. How—"
"It's based on the will to sacrifice. The willingness of a wizard or witch to die to protect another. It's almost impossible to make one, as generally when you sacrifice yourself, you stay dead. Usually, all that is left is an echo."
"That's it, isn't it, Professor? My mother's spell?"
Severus' eyes met Harry's quickly; then they looked away just as fast.
"Not exactly. The spell your mother cast had no specific direction. It was involuntary magic. Extremely powerful, but involuntary."
The three of them went back to watching the shield, which was slowly fading from view.
"No one who intends to harm you or anyone else in the castle will be able to get through," he announced, pleased.
He stopped looking up, turned and walked towards the entrance of Hogwarts, Harry and Professor McGonagall watching him.
A few steps ahead of them, however, he stopped. He clenched his fists as if preparing to do something extremely painful.
"Well done, Potter," he said without turning around, and continued walking.
[1] "Enagisis" is based on the ancient Greek concept of "enagisma" (ἐναγίσματα). In ancient Greek religion, it refers to a ritual sacrifice offered to heroes or the deceased.