A/N: This was written as a contest prize at deviantArt. Hope you enjoy it.
He was in control now.
He watched, from his throne-like chair in the middle of the high table, as the students filed into the Great Hall. Students of Hogwarts, of his school. The corners of his thin mouth twitched upwards slightly as they began to notice him.
The Slytherins, of course, looked delighted to see who was now occupying the Headmaster's chair. The other houses, however, did not look so happy. The Gryffindors, and Potter's friends and cronies in particular, looked nothing short of outraged. But it didn't matter. They didn't really matter. Severus was finally the master of his own destiny, rather than a pawn of Voldemort or Dumbledore. He had power. He had position. He had the title of Headmaster of Hogwarts, and all that came with it.
Amycus and Alecto, seated on either side of him, had also begun to notice the students' reactions.
"Longbottom looks like causing trouble already," whispered Amycus. "And the Weasley girl... Should have finished her off in June..."
Severus' eyes found the pair Amycus was describing. Both were looking straight back up at him from their table, surrounded by a knot of other members of that ridiculous gang Potter had formed nearly two years ago. "Dumbledore's Army," thought Severus grimly, "didn't do him much good in the end."
Potter himself, of course, was not there. Not even he would have been stupid enough to attempt to return to Hogwarts; he probably wouldn't even have made it onto the train. Well, he might have been foolish enough; thankfully Granger wasn't, and she was with him. Or so Severus presumed, as she was not there either. Being a Muggle-born, she too would have not been allowed to enter the castle. The youngest Weasley son was absent, too; Potter, it seemed, had taken his sidekicks with him.
And so, thought Severus, the head had been removed from the snake. Or rather, the lion. Without Potter, Weasley and Granger to lead them, he doubted very much that the remainder of those who might have caused trouble for him would find it within themselves to do so. A number of them looked hurriedly down at their plates as his dark eyes swept over them. He smirked. So much for Gryffindor courage.
And yet, it wasn't the sense of power over the students that gave Severus such a sense of satisfaction. That was something he had enjoyed for years now, and although he was now Headmaster and that power was greatly increased, it still wasn't anything particularly new.
What was new was that Severus was finally and completely his own man again. For this first time since the night in Godric's Hollow, even since Severus had first joined the Death Eaters, he was the one making the decisions. He was free, quite free to abandon Dumbledore's plans and schemes if he wanted, impose Voldemort's regime on Hogwarts, and wait for Potter to be captured. He could choose not to give Potter the sword, not to tell him that he needed to die in order for Voldemort to be able to die, and ensure that the Order of the Phoenix was crushed by the Death Eaters.
But as visions of dark glory filled his head, as Severus saw in his head the victory of Voldemort and the Death Eaters, with himself at the Dark Lord's side, they all faded, to be replaced with an image of a face. Her face.
She had hated the Dark Arts. It was that, more than anything, that drove them apart. Something inside of him still believed that there might have been some reconciliation after that horrible day in their fifth year, where he had shouted unforgivable words at her in painful humiliation. There could still have been a way back, had it not been for his already overwhelming affiliation with that which she despised.
It was only after she had died that he saw the truth behind it. If Voldemort had spared her, like he had promised he would, Severus had been convinced that he could have shown her, convinced her, that the aims of the Death Eaters were for the good of everyone in the end. But he knew better now. He had experienced for himself the pain they caused, the complete devastation their actions inflicted on others lives, for he had lost that which he loved. She, whom he loved. There were, after all, fates worse than death. Life, for example. Living with loss.
And still, all these years later, it was still her who prevented him from relapsing into his old ways, and being tempted by the dark side again. The image of her face acted as a balm, quenching the fires of furious desire for power that had suddenly erupted within him.
He would still keep going. He would still continue to defy Voldemort, to lie to him, weaken him, undermine his position from under his very nose. He would do his best, without arousing suspicion, to protect the students of Hogwarts against the tyranny that the Carrows would surely try to bring down upon them.
Ultimately, he would find Potter somehow, and deliver him the sword of Gryffindor, currently safe in his office. Later, after watching and waiting for the time when Voldemort seemed, inexplicably, to fear for Nagini's life, he would tell Potter, somehow, that which Dumbledore needed him to. He would continue along the path that Dumbledore had set for him, despite a lurking feeling that it would lead to his end. Few wizards got away with deceiving Lord Voldemort once, let alone continuously for over three years since his return. Severus knew his luck had to run out at some point.
And yet, he would keep going. Not because he owed it to Albus Dumbledore, or because he had no other choice. He was finally acting according to his own will. He would keep going because he wanted to. Because he wanted to see the end of the wizard who killed Lily Evans, and he finally had it in his power to make it happen.
Some might have said that it didn't matter that he made the choice for himself. But the very fact that he could have turned his back, abandoned the plan - the very fact that he could have chosen otherwise - was enough for Severus Snape.