The owls had come in the morning. Hedwig had returned from Hermione's house with a book, of course: How to Apparate - A Beginner's Manual; Pigwidgeon had brought a birthday cake, some meat pie and tons of sweets sent by the Weasleys; Hagrid had sent him a Moke-skin moneybag (Grawp had killed a Moke, and Hagrid, mortified, decided to use its skin for a good cause).

Harry had spent the afternoon in the most complete boredom. Finally, he was of age. Big deal. Nothing was going to change in his life. Except that now he could learn to Apparate, and Severus wouldn't need to take him in his arms when they needed to go from one room to the other in the cottage. But it had been a long time since they had done that. And Harry liked to be held by Severus when they Apparated.

Ah, Severus. Severus hadn't shown up for almost a week. Hadn't he promised to come at least twice a week? Had something happened to him?

Boredom was turning into concern when Snape Apparated onto Harry's bed, precisely on top of him.

"Ow! Git, mind your landing! Do you think that you're weightless?"

Snape didn't even care to glare at his lover, or to roll off him. On the contrary: he eased himself on top of Harry.

"What kind of reception is this for a special guest? Do you want me to go?" he murmured in Harry's ear.

Harry smiled, happiness finally reflecting on his face.

"Happy birthday, brat."

"Oh. You did remember it."

"I also brought you a present."

"Really? I wasn't expecting that..."

"It's not every day that you reach the age of consent," whispered Snape, before capturing his lips in a searing kiss.

Some kisses later, when Harry was sure they would remain in bed and... proceed with what they were doing, Snape pulled back, sat on the bed, produced a package from his robe and handed it to Harry.

The wrapping paper was laminated and seemed impregnated with magic. Harry opened it carefully. Inside, there was an ancient, yellowed book: Hierosgamos, by Asklepios Arrheton.

Harry raised his eyes to Severus, puzzled.

"I marked a page for you to read. Do it now," ordered Snape.

Harry browsed the book and found a peculiar page marker: a tiny green satin serpent. The marked page belonged to the chapter named "Primi Gradus". In a cryptic, hermetic language, the page described a... betrothal ceremony.

"Er... Why... What..."

"Don't you understand yet?"

"You know, I'm not really brilliant."

Severus glared at him. "Today you are reaching the age of consent. This event doesn't make our relationship legal, because I am still your teacher. However, symbolically, it means that now, and only now, you are considered able to consent to our relationship."

"What a heap of crap. What's the difference? Yesterday I couldn't and today I can?"

"Yes, all those limits are arbitrarily set. But this symbolic meaning is important, magically speaking. It means now you are able to..." Snape seemed surprisingly embarrassed "...to agree to a... commitment."

Comprehension started to dawn on Harry. "Commitment... And this book... You are asking me to..."

"It is analogous to what is called an 'engagement' today. However, what I am suggesting is that we follow this ancient rite of mutual commitment, which is the Primi Gradus of the Hierosgamos. 'Hierosgamos' means 'sacred marriage'."

"Oh! And what do we have to do?"

"It's quite easy. We only have to join our hands, palms together, facing each other, and pronounce the vows written on that page."

~* ~* ~

With joined hands, both pronounced their vows, first Harry, then Snape - who had his eyes fixed on Harry's while repeating the incantation:

"Otoved elh euq otnemitnes oa leif etnematulosba e ele a orecnis ieres euq, zilef oriecrap uem ranrot arap odut ieraf euq ed ahnumetset omoc adiv a ocovni."*

As soon as Snape pronounced the last word, a ring materialised on their fourth finger of the right hand. It was a sterling silver obsidian ring. A magical ring. A feeling of infinite bliss and union with his partner spread through Harry's soul. Snape smiled, and withdrew his hands. As in a trance, Harry gazed at him, intrigued.

"It is done. Only we can see these rings. That magical influx you felt was exchanged only between us. This ritual has no external meaning, except for the fact that it enhances our magic indirectly. The rings will remain with us as long as we keep our vows. If one of us breaks the vows, the rings will simply disappear, and our magical union will be broken."

"So if you cheat on me I'll know right away?"

"You have to understand, Harry, that it doesn't mean I cannot have sex with another person, provided that I keep my vows."

"How come?"

"Sometimes, under certain circumstances, as a spy, I have no choice."

"Argh. I... understand. And I don't want to know about that. "

"That's understandable. I'm sorry if I literally broke the magic of the moment. I just wanted to make this clear between us, because the vows we made imply this sincerity."

"And what about this sacred marriage thing?"

"One day, when we are not teacher and student any more, and when we both are free from all these chains that bind us to Lords and Masters and prophecies, we might perform the ritual that will bond us for life," said Snape, in his low, deep voice. "It's a very complex ritual. You can read about it in the book."

Harry felt a strange peace. Severus made him feel safe. For the first time, he trusted another person completely, and that was a wonderful feeling.

They made love once more on the bed of the tiny room with bars in the window. Amazingly, now that room didn't seem like a cage to Harry any more, but like an airfield from which he could take off and fly high into the sky.

NOTE:
* Approximate translation: "I call Life to witness that I shall do everything in my power in benefit of my partner, and that I shall be absolutely loyal, sincere and faithful to the feelings I devote to him."