"Snape! He trusted you!" Roared Harry, advancing in on Snape, wand raised, several spells ready to cast. Among those spells, none of them were innocent, nor legal.
Severus Snape, the man who's veins and mind were assaulted with pain and grief completely understood and properly feared the rage and anguish within Harry's voice. Pain that shouldn't have ever been known to someone so young. But living in this world, this cruel unforgiving world led both of them to losses that ingrained itself within their souls. And as Severus briskly strolled over the grounds of Hogwarts, his heart broke into pieces, knowing that he, just like Harry, was on his own. No more Dumbledore... the man who he had come to know as a friend. The only friend he had known in his entire life. But it was a part of the plan. Part of the plan to stop the mad Dark Lord from taking from everyone what he had taken from him.
A spell flew his direction. He easily blocked it. The rage the boy was feeling was blocking his mind, stopping him from thinking clearly and casting actually effective spells. Naturally. He used to be the same way with the boy's father. Unfiltered rage at the man who had made his life a living hell during school. He would have given anything to have seen that same emotion in him. But now that he saw the dead man's son filled with that emotion, it brought no satisfaction, no smirk, no sneer, no happiness, only grief and pity.
"Coward! Fight back!" shouted the enraged boy, shooting another spell, only to be blocked and retaliated by Bellatrix.
"No! He belongs to the Dark Lord." He spoke, feeling disgusted at the words that he was supposed to speak in order to keep his cover. He wished he could turn on Bellatrix and blast her, ending her and her cronies here and now. But he knew that it would make no difference to the Dark Lord. Some other worshipping fanatic would take her place and amass the same amount of power she once had. He had to remain if he wished to cause any significant damage to the Dark Lord's cause.
Harry struggled to pick himself up, bursts of dry sobs escaping his mouth. He lifted his wand once more. "Sectum Sempra!"
Only to be blocked and reflected a stunning spell.
Snape knew he should have felt anger, annoyance, anything at the boy for using his owns spells against him, but nothing came to him. He had masked his true emotions, something he had done since childhood, and now that he needed them to stay hidden, they seemed to burst out of him. Instead of letting his grief through, he hid it with disdain.
"You dare use my own spells against me, Potter?" He emptily sneered, leaning over the fallen boy who was trying to pick his wand up.
If having to kill the only friend you ever had could break your heart, having the eyes of the woman you loved looking back at you with pure hatred utterly shattered it. In the eyes of this boy, he was a monster. A monster who had taken his mentor, the man who had come to save him from his life of torment. A man that showed him that a whole world of beautiful magic existed. A man who showed him that there was always room for kindness and love in everyone. Snape had taken that from him, Snape knew that. And Snape knew that he had to continue being that monster in order to maintain the boy alive... to maintain Lily's eyes alive, despite them being filled with hatred. He was a monster, he knew that, he would always be a monster. So...
The monster sneered. "Yes, I'm the Half Blood Prince."
Harry couldn't do anything except stare at the monster leering over him. Snape, meanwhile, simply kicked away Harry's wand and turned to leave.
Severus Snape was a monster, he knew that. But now, the war was beginning, the time for grieving had passed a long time ago. So, as he left behind the castle that had become his home for a very long time, he found himself praying for the son of the man he despised.