A/N: While this is about all four of the Marauders, the focus is on Sirius, as he was in his prime: fiercely loyal, a little hot-headed, quick to act and a prankster as much as he was a defender of justice.

Sirius Black: Marauder

The corridor was alive with activity in the raucous between classes as the four Marauders made their way to Transfiguration. Severus Snape was walking a little ahead of them, greasy hair hanging limply as he whispered with his friends. While James had his back turned to catch a glimpse of a certain red-headed witch, Sirius' eyes lit up with a grin while he pulled out his wand.

Wordlessly, he sent a Locomotor Mortis flying towards the slimy Slytherin, and burst out in a fit of laughter as their classmate fell face first to the floor. James turned, made curious by the commotion, and grinned while he patted his old friend on the back.

"Nice one, Padfoot, very well done," he said, while Peter laughed along with them. Remus merely looked up and shook his head with a roll of his eyes, though he could not deny the tug at the corners of his mouth.

Snape stood and brushed himself off before marching over to the Gryffindors, temper bubbling over as he drew his wand.

"You'll pay for that, Black!" he spat, eyes bulging in his embarrassment.

"Oh yeah? What are you going to do? Wipe your nose on me?" Sirius taunted, causing the usual palour of the boy's face to turn a little red in anger as a vein throbbed in his neck.

"Or you could shake like a dog to loosen some of that grease in your hair on us!" James suggested, causing the four boys to laugh as if they were in on a joke that Severus didn't understand.

Severus took a deep breath in, ready to loosen a string of obscenities at the four boys in his hatred of them.

"Severus, leave it," came a soft voice from behind the Marauders, and they all turned to see none other than Lily Evans interrupting the fierce battle of testosterone. On sight of her, Severus swallowed his words and stormed off back to his friends in a silent rage.

"Evans, nice of you to join us!" James commented with a grin, unable to stop himself.

"Oh, bugger off, you conceited halfwit!" she shouted, immediately annoyed by his presence. She stalked off, red curls bouncing with her steps.

"Well, that went well," James shrugged before continuing the walk. His friends followed, Sirius turning to him with a lazy smile.

"She'll come around eventually, Prongs," he consoled his friend.

When they rounded the next corner, however, their smiles faded. Mulciber, tall and imposing with hair as black as night, was rounding on Mary McDonald, the happy-go-lucky, heart on her sleeve Gryffindor. Sirius immediately felt the hackles rise on his neck, and was glad he hadn't pocketed his wand just yet.

"Watch where you're damn well going, you filthy Mudblood!" he said, standing over her with his wand inches from her face, sparking. He had her backed against the wall and despite the stubborn look on her face, the way she leaned away from him betrayed her fear.

Sirius came up behind him slowly, keeping out of his line of sight, and pressed the tip of his wand into the larger boy's back.

"You should watch who you pick on," Sirius retorted, his voice dark as his eyes set, as if a storm was brewing in their depths.

"You don't scare me, blood traitor," the older boy retaliated, turning to face Sirius as his attention on Mary faded. He had a new enemy now.

"Then I'd suggest you're afraid of the wrong people." Mulciber's eyes were fixed on Sirius as he sneered. As James stepped forward a little, he moved his gaze a little to take in the scene before him. Three wands were behind Sirius', trained on Mulciber with concentration and loathing in the eyes of their holders. Mulciber was alone, his friends not behind him to back him up. This was not a fight he would win.

"What in Merlin's name is going on here?" came a shrill voice down the corridor, as loud, precise footsteps echoed nearer. Sirius didn't need to turn his head to know it was McGonagall.

"Mulciber was threatening Mary, Professor. We were politely suggesting he ought to move along," Sirius explained, his eyes never leaving Mulciber for a second. Mary nodded at McGonagall from her corner behind Mulciber.

"Twenty points from Slytherin and Gryffindor for disruption in the hallways. Mr Mulciber, on your way," she snipped. Mulciber threw the Marauders a black look before heading towards his classroom.

McGonagall turned to the four boys as they turned to her, hiding their wands as quickly as they had been drawn.

"Ten points to each of you for displaying courage and loyalty towards your fellow Gryffindor. Only, if there happens to be a next time, try not drawing your wands," she remarked, the hint of a smile dancing across her face as she turned and left them.

"Well, that's alright," James grinned, and Sirius mirrored his friend's expression.