A not-so-vague Disclaimer: I don't own Harry Potter or the Buffy quote (prize for whoever spots it)
Sirius grabbed Remus' hand and led him out of the packed common room and out into the halls.
"Thought I'd give you your present." He whispered in the werewolf's ear, despite himself, Remus shuddered as his warm breath teased the tiny hairs around his ear.
"This isn't a present of a sexual nature, is it? Because as much as you know I'd enjoy it I doubt James would be happy with us leaving my party for, as he calls it 'sexy funky fun'." Sirius gave him a strange look.
"Not everything's about sex, Moons." Remus laughed at this.
"Really? I didn't think you were aware of that. Merlin, you've changed a History of Magic lesson into something sexual." Sirius' ears turned pink at the memory of that and Remus had to grin, while he tried to maintain that he didn't blush at anything, Remus was very good at making him blush. Not in embarrassment, Sirius was far beyond that, but in remembering the more… interesting aspects of their lives.
"C'mon, it'll be midnight soon." Sirius half dragged him through the halls, paying no attention to the werewolf's protestations that he was dislocating his wrist. They came to the room of requirement and Sirius grinned before opening the door. A bed was made with clean white sheets and bathed in the soft glow of candlelight. Next to the bed was a pot of ink and a calligraphy brush. Remus raised his eyebrows.
"So you're going to teach me Mandarin?" He joked.
"Nope, take your top off." Sirius said, sitting on the bed.
"It's my birthday! Why aren't you doing a weird ink striptease for me?" He protested. Sirius gave him a tired look and he conceded, grumbling as he stripped off his t shirt. "Now what?"
"Lie next to me, on your stomach. Here, put a pillow under your chin." Remus did as he was told and Sirius took a piece of parchment out of his pocket and smoothed it out on the bed. Remus shuddered when he felt the brush on his back and he realized Sirius was writing something. The scars on his back tingled when the ink moved over them and he smiled and closed his eyes, losing himself in the feeling of the wet ink on his back. As a child he had loved having his mother brush his hair, enjoying the attention and the sensation of the brush on his scalp. After she died, nobody ever touched him or bothered about his appearance beyond making sure his clothing was clean. Nobody but Sirius, that is. What felt like a few minutes later Sirius stopped writing and he mumbled in protest.
"It's done, Moony." Sirius sprinkled something on his back and he felt the ink warm. He finally realized what Sirius had been doing.
"You did a spell." He said, sitting up.
"Something I found, I thought it would be a good idea."
"Something you found? Was that what you were doing in the library with Evans?"
"Why else would I be there? It's not exactly interesting."
"What does it do?" He asked. Sirius smiled.
"Protects you, its old magic, earth magic." Remus' eyes widened.
"But that was lost, nobody can control it anymore."
"Are you doubting my ability? I'm Sirius Black, nothing's impossible for me." He grinned.
"It could've damaged your core," Remus protested.
"It was worth it." Remus finally shut up and kissed him.
"Oi, I expect more gratitude than that!" At that, Remus pulled him down on the bed. All in all, it was a very good eighteenth birthday.
Author's Note: I was going to put an ancient Greek/ Latin poem into this, but couldn't find an appropriate one. Based on Willow writing the Sapphic poem on Tara's back in 'Restless' (BTVS S4)