Sectumsempra

Disclaimer: JK Rowling owns the Potterverse, and the characters, of course, unless I end up coming up with any original ones. And I'm not making any money on this.

The fool had once again left Severus armed, even though he was upside down. Liberacorpus, he thought, and this time, being prepared, he landed in a squat instead of a tangle. Potter's Vanishing Spell flew over his head. Severus sent another silent Sectumsempra to Black and now he also had a slash on his face. Both golden boys were marked.

Before he could do anything else, Potter disarmed Snape with another Expelliarmus, this one bringing Snape's wand to Potter. At the same time, Black tied him up in ropes, with an Incarcerous.

"Any last requests, Snivellus?" said Black, grinning maliciously, pointing his wand at the Slytherin.

Remus decided this had gone far enough; Snape hadn't landed a single hex and now he was disarmed and tied up. Time to call it quits. He walked over to Sirius and James and then gasped as he saw their faces.

"James, Sirius, you're bleeding!" he said. "Look at your faces!"

Sirius conjured a mirror and looked at his face, handing it to James, who did the same. They both cast simple healing charms on the cuts, but the gashes did not close up, or stop bleeding.

At this, Lupin jabbed his wand in Snape's chest. "What did you do, Snape? What did you hit them with? Why aren't the cuts closing?"

"It's a little curse of my own. The cuts will close in a little while with no harm done, just a little scarring."

"You bloody bastard," shouted Sirius, suddenly contemplating a scarred face. James was deathly silent, contemplating the same thing.

"Be quiet, Sirius!" Remus said. "OK, Snape, it's your curse. So what's the counter-curse? To prevent scarring?"

"Are you asking me to perform it? Because I'm not going to teach it to you."

"Fine, then perform it yourself."

Snape stood there, silent and smirking, waiting.

Remus suddenly realized they'd have to set him free and looked over at James and Sirius.

James released Snape from the ropes and then growled to Remus, "Give him his bloody wand back."

Remus threw Snape his wand, as if he were trying to hit the Slytherin with it.

"There's just one condition," said Severus. "It's been fun so far, but I'm getting rather annoyed with being attacked 'just for existing', as you so eloquently put it, Potter. I must insist that you promise not to make any more unprovoked attacks on me."

Silence. Severus stood there waiting.

"We won't make any more unprovoked attacks on you," muttered James. "I promise."

"You too, Black."

"Me either," said Black.

"Say it," insisted Snape.

"No more unprovoked attacks on Snivellus," he growled. "I promise."

There were some nervous giggles from the crowd at the nickname and Severus frowned, but decided to accept it.

He went first to Potter and traced his wand over the gash, muttering an incantation that sounded almost like song. Then he pronounced a gentle cleansing spell that he had learned from Madam Pomfrey. James' face was clean, showing no sign of the cut. Then he went to Black and repeated the procedure.

Without another word, he turned his back on the Marauders and went over to where he had flung down his bag. He swung it over his shoulder and went up to the Castle and his dormitory.

Severus knew he was in trouble. If Avery had been upset about a few harmless hexes on a half-blood, he'd be furious about slashing curses on two pure-bloods. In front of a large audience. If he had already managed to transfer to Rosier, he didn't think Evan would mind that much. But now, for all he knew, he'd just made that transfer more difficult. The last thing Rosier would want was a fight with Avery, which indirectly meant challenging Lucius himself. And he hadn't even come up with a way to get the Felix yet.

Violently, he threw himself down on his stomach on his bed and buried his head in his arms. A very large audience. Potter had exposed him in front of the whole school, not once but twice, using his own spell. Embarrassment warred with rage to make his face flush.

He was used to being humiliated, first by Black and company inside Slytherin and then by Potter's gang outside. He'd always taken it matter-of-factly before, just part of being low-blood and working class and poor. He had never expected life to be fair. So why was he reacting like this now?

He sat up. It was Avery he needed to be thinking about. Avery and Rosier and getting his hands on some Felix Felicis.

Avery was terrified. He had watched the whole thing with amusement until he realized what Snape had done. Attacked two pure-bloods. Drawn blood. After he'd just been called to task over hexing Jorkins. What was he going to do? For the time being, he ignored Snape while he considered what his next move should be.

Author's notes:

I got the counter-curse from HBP where Snape uses it on Draco after Harry uses Sectumsempra on him. Snape mentions scarring. I added the part where scarring was part of the curse itself if not correctly countered.