Disclaimer: I own none of the characters.

Previously...

"The cost…" Magnus whispered. "Alexander… No matter what, you are a Shadowhunter… It may be too much for you…"
Alec's eyes widened again momentary as he realised his former speculations were probably mistaken. "Please tell me."

Magnus bit his lower lip looking at him worried. "Let me start at the beginning. This spell is the hardest one I have ever encountered, but I know I am strong enough to do it. As long as you want me to…"

"I do…" Alec nodded. "What is the price?"

Magnus sighed softly, looking a little relieved but not completely yet. "I managed to find the spell in a really old book and some of the details are lost… I understood the basics though. About the price…" Magnus trailed off.

"Yes…?" He said anxious to know, his voice a low whisper.

"For this spell to take effect we both must pay a price. It works by transferring half a Warlock's magic to someone else; by making him essentially, a Warlock too. Thus immortal. Thus the price you have to pay."

"Which is?"

Magnus studied him for a moment, then smiled sadly running a hand over his face, pointing to his eyes. "A demon mark. Once you become a Warlock it will appear on you. It is a huge risk, as I have no idea what it may look like… It could be something subtle, or it could be wings. Or even your skin changing colour…"

Alec raised an eyebrow. "Aaaand? What else?"

"What else? What do you mean? Isn't that enough?" Magnus exclaimed surprised before he could stop himself.

"But you said I'm a Shadowhunter and the cost may be too much for me because of it…" He trailed off and then it seemed to dawn on him. "Oh… I'm losing my marks too after all, aren't I?" He asked trying not to sound disappointed about it.

"What? No!" Magnus said immediately. "This ceremony keeps your true nature intact! It just adds some of my fabulous powers to yours."

"Oh? I was certain I would…" Alec trailed off.

"And you'd accept that?" Magnus asked him, his cat eyes wide.

"Of course…" He answered without losing a beat. "I told you I'd do anything for you…"

Magnus was staring at him in awe. "You would even do that?"

"I would." Alec smiled. "But… If that wasn't it, what did you mean about the price being too high for a Nephilim?" He asked confused.

"Alexander… No Shadowhunter would normally accept that. To place a demon mark upon himself or share anything with a 'disgusting Downworlder' like me." Muttered Magnus. "Not even in order to be immortal."

Alec looked scandalised by his words, angry at his people for their attitudes and Magnus went on, to soothe him.

"But in a sense you have already done that, right?"

Magnus smiled shyly at him squeezing his hand and leaned a little closer. Alec smiled back at him his anger fading because of Magnus' smile and touch, and kissed him.

"And I always will."

Magnus smiled again, relieved. "My Alec… I didn't know if I should tell you and it was killing me… I had finally found a way but at what cost? How could I ask you to sacrifice anything for me? I want to give you things not take them from you…"

"It's okay…" Alec whispered squeezing his hand again. "This is no price at all…"

"Alec." He said gravely. "It's not as unimportant as it seems. A demon mark could be either something subtle or prominent… You could grow wings for Angel's sake! I have no idea how the spell works, and it terrifies me… And what if they it is something too obvious? You may really lose your marks…" Magnus was muttering now, panicking again.

"Magnus, Magnus, calm down, breathe! It's going to be okay, we're going to be fine. I will conceal it and they won't know. And if it's something I can't hide, my Magnificent High Warlock boyfriend can help me and "glamour it away" so no one will find out." He smiled touching his face softy. "Right? Don't worry…"

Magnus smiled at him relaxing a little, but it was short lived. "There's more…"

Alec's eyes widened momentary, but he regained his composure immediately. "Of course. Tell me." He said steadily, his eyes never leaving the Warlock's, their hands intertwined.

Magnus however, dropped his eyes from the Nephilim's, hesitating again. The boy softly touched his face soothing him, then pushed his chin up to make him look at him. "It's okay Magnus… You can tell me…"

He sighed and nodded. "Alexander… Remember. You don't have to do anything you don't want. I am just giving you an alternative option, this is your choice alone. I will never force you to do it, and no matter what you choose, my feelings for you will never change. If you don't want to do it, I will understand. It's too much of a burden after all…"

"Magnus…" Alec interjected, smiling at him softly. "I know… You don't have to worry…"

"Alec. You're taking this too lightly! It's a serious matter! Immortality isn't a game… It's can be a curse… And I'm afraid to do this to you…"

"Then why did you look for a way in the first place?" Alec whispered, his voice wavering.

"I didn't think about it much before… I didn't dare hope…"

"Think of it now then." Alec said darkly. Magnus didn't understand why his tone changed suddenly but then the boy went on. "Think about it first before telling me to choose. Are you sure you want to spend eternity with me?" He asked misinterpreting his Warlock's hesitation.

"Wha…?" Magnus muttered staring at him with wide eyes. "Alexander what are you saying?"

Alec looked at him but then dropped his eyes looking away. "You talk about me, and how this is my choice… But what about you? Isn't it your choice too? It's your powers we're talking about. It's your life too. Won't you change your mind?"

Magnus looked at him sadly. "Alexander… I have been waiting for you, for hundreds of years…" I would give up all my magic for you, not just half of it. "Now, that I finally found you, I am never letting you go again. Once was too much." He said, pained by the memory.

Alec bit his lip and Magnus went on.

"But you know…" He whispered referring to their break-up. "Even if it hurt us both unbearably I'm glad I did it."

"What? How can you say that?" Alec asked surprised, thinking of all the pain they both endured. "How could it have been worth it?"

"As the song goes baby, 'Have no fear, there are wounds that are not meant to heal… And they sing, in Venere Veritas…' "

"In love there is truth*…" Muttered Alec.

"Exactly… I'm glad I did it because I realized that I can't live without you… Because I will never forget this kind of pain and emptiness I felt while we were apart."

While Magnus was talking the Shadowhunter's eyes never left his, as he listened carefully to every word he said, his expression changing, from the dark sad one, to one of pure adoration and love laced with anguish, only for him to smile again lovingly at the end looking at him dazed, his heart beating faster.

"I love you…" He whispered.

"I love you too baby…" Magnus smiled, and leaned to kiss him softly.

Alec wrapped his fingers on Magnus' dark locks holding him closer and kissed him with abandon, forgetting everything for the moment, losing himself in his lover's touch.

Did you like the idea for the immortality cost? (There's more!) Next chapter soon!

The song Magnus is referring to is "In Venere Veritas" by H.I.M.

Also, I am aware this (*) may not be entirely correct… Most say it means in sex, not love, but there was also that answer so I went with it:
"Venere comes from the Latin word Venus. The Roman goddess of desire, sex and love.
So, In desire/sex/love there is truth."

(FROM GOOGLE ANSWERS)