Well, this is my first story to be placed under the crossover section. It is also the first story involving ID characters. It takes place after CoFA and contains spoilers from CP. Mind you I'm not even half through so mistakes might have been made whenever I mention events from CP. I also include events that would take place during or after CP2 so let me make this very clear: I MADE THEM UP! Okay? Now I will proceed with this story which is yet to be named. By the way, it is a one-shot. Read On!

Tessa crept up the stairs to Magnus' loft. It was three in the morning, he was sure to be sleeping. Unwilling to disturb him, she instead Changed. She had had to change into him once for some reason or another that she no longer remembered. From this she gained the knowledge that Magnus kept a spare key. It was, of course, not under the mat. Instead, it was hidden behind one of the bricks. Having removed it, Tessa unlocked the door and crept inside.

Magnus was asleep on the couch with a boy lying on his chest, asleep also. They were both without a shirt and she could see that the strange boy had pale skin that covered tight muscles. One look at his face made Tessa have to hold in a gasp. He looked just like Will. The same black hair and a similar face with the shadow of the blue behind his closed eyes. His mouth, which was pink and inviting- like Will's- hung slightly open.

"Magnus," she whispered. She had long since changed back to Tessa so it was not a mirror of Magnus standing in front of him when his eyes flashed open. He slowly slid out from under the boy, careful not to awaken him.

"Hello, Tessa. It's nice to see you." He hugged her and held her tight.

"It's nice to see you too." They stayed like that for a moment before Magnus invited her to be seated on the other couch across from the still sleeping Shadowhunter.

"I see you've moved on from me," Tessa commented jokingly. Magnus turned eyes full of love on the boy and nodded. They had had a brief affair once, about fifteen, maybe twenty years ago. It never went very far and had ended with mutual consent. They were no less friends because of it. After all, they needed each other. When his new lover departed this world, she would be all he had left, as he was when Will had died.

"I have."

"Is he a Herondale?" Magnus shook his head.

"No, a Lightwood. Alec Lightwood."

"A Lightwood?" she inquired, astonished. Gabriel, Benedict, even occasionally Gideon- jerks.

"He's not like that," Magnus replied defensively. "He's not like any of the other Lightwoods. Now, his sister, on the other hand…" He trailed off. Tessa smiled, shock dissipating.

"It's good that you've on. I'm no good for you," Tessa said, winking.

"Oh, you're plenty good for me. Just not in that way. And, I may have moved on, but I never will again." Magnus whispered that last part. Tessa nodded, understanding. It had been thirty years without Will, and she still cried sometimes and she had never loved anyone since. She understood.

"I understand. And because of that, I will give you advice."

"Please do."

"When he dies, you will be crushed. It will kill everything in you, even worse that the day you realized Camille was never to return to you. The morning I found Will dead in our bed, after almost seventy years, I was tempted to break the Law so the Shadowhunters would kill me. But, then I thought of you and of the words of my letter so many, many years ago. You needed me. So, when that day comes, call me. I'll step through the nearest portal and be here. But, he would want you to live." The last part were words she told herself everyday. Will would want her to live. Magnus nodded.

"I'll remember." Then he said softly, "Alec wants to become an immortal." Tessa swallowed back her shock.

"I can't help you with that decision. It's up to you and him." Magnus smiled sadly.

"I know. A selfish part of me wants to, wants him to be mine forever. But, the other half is telling me that it is wrong to be so selfish." Tessa just nodded, not knowing what to say. "So, how's it feel to be home?" Magnus asked, abruptly changing the subject.

"Lonely," she answered. Magnus raised an eyebrow, begging for clarification. "Will always wanted to come. We never got around to it. So, I look at everything and both see my home as it was and think of what Will would think. Everyone I might've known died." She ended her explanation with that.

"One of his family is here." The words shocked Tessa. She lifted her head and stared him in his incredible eyes. "His name is Jace, and he lives in the Institute. He looks nothing like him but he has his personality." Tessa grinned.

"That's amazing." Magnus grinned.

"I can make the news even better."

"How?" Magnus pointed to Alec.

"That's his parabatai." Tessa laughed aloud. Magnus snapped his family, showering blue sparks. A book appeared on the table. He opened it to a page that was titled "Herondale". It was the Shadowhunter families book. Magnus pointed to a spot near the middle of the page.

"Cecily." Tessa nodded. "She married Charles Graymark." Tessa nodded again. She knew all this. "They had one son name Alexander Herondale, who the chose to carry his mother's maiden name, knowing that you and Will could have no children but Charles had two brothers. He married Alice Wayland. They had two children- Alicia and Richard. Richard married Lilith Penhallow. They had two children, Alexander and Mary Lynn. Alexander moved to America, which is where I'm assuming you lost track of him." Tessa nodded. Magnus grinned. "But, I didn't. Alexander married Maryse Starkweather, who became the Inquisitor. Anyways, they had one son- Stephen. Stephen first married Amatis Graymark. He then divorced her and married Celine something-or-another. They had Jace," Magnus concluded. Tessa nodded.

"So many people," she said.

"That's what happens with mortals." Tessa looked at him. "But, even immortals face death eventually." He was obviously commenting on her contemplation of suicide.

"Thank you Magnus." She suddenly remembered thee oath they had sworn at Will's funeral. She spoke it aloud. "Through joy and sorrow, through tears and pain, through blood and death, I'll be there for you, Magnus Bane."

"And I for you, Theresa Grey." She smiled.

"The sky lightens, my dearest friend. I must go." They hugged and then she walked out the door. When the door closed, Alec opened his blue eyes.

"Who are you talking to?" he said sleepily.

"An old friend," Magnus replied.

"A friend?" Alec asked, enunciating the word friend. Magnus smiled.

"We dated for- oh- a month? It didn't work out. But, we need each other. For if there is no one in the world who cares for you, do you really exist at all? She is a warlock, an immortal. I've known her since I dated Camille." Alec just nodded, opening his arms to him. Magnus curled up next him and they both fell back asleep.

So, that's that. I liked it. It was just an idea I had. Hope you like it. Done writing, StevieRae2011, signing off!