Disclaimer: I do not own the Doctor, the TARDIS, the Great Old One, or Lauren Bannister. They are owned by BBC and Bryan Davis respectively.
AN: All dialect in [ ] is translated from Gallifreyan, which the TARDIS does not translate for human ears, but for the purposes of this story, I have written the dialect in English.
The TARDIS hummed with energy as the Doctor walked around her console. It always felt good to have her thief running his hands across her parts. The Doctor was so much more than a pilot to her, he was her friend. The TARDIS always wanted her thief to be happy, but there were days when that couldn't be helped.
On this day, she could sense that the Doctor was confused. It had been two years since the anthrozil Lauren Bannister had started travelling with him, and in that time he had fallen in love with her.
At first, he hadn't understood what the feeling he had for her was, but over time he figured it out. Her smile made the entire room brighter, her long brown hair seemed to cascade like the waterfalls of Midnight. Lauren's very presence made the Time Lord's hearts beat wildly. Even so, he could not love her. She was human, and he was a Time Lord: ageless, forever living until the day fate brought him once more to the Fields of Trenzalore. He would continue living, but Lauren would age, and she would die. The very thought of Lauren dying because of him made the Doctor's hearts tear.
The TARDIS could sense the Doctor's pain, and wanted to help him, but didn't know how. She had grown fond of Lauren as well, and saw how happy she made the Doctor. The TARDIS also knew a secret: Lauren loved the Doctor. When Lauren was alone, she would often talk of the Doctor, and her feelings for him. The TARDIS' matrix swelled with joy at hearing that news, but saddened knowing she couldn't do anything about it.
The Doctor continued to walk around the console, one hand gently stroking it as he thought of Lauren. A part of him wished he had the Gauntlet of Rassilon, a device that could give anyone the DNA of a Time Lord. But when the Doctor put serious thought into it, he knew that he couldn't do that to Lauren. If she became a Time Lady, she would have to watch, ageless, as her family and friends all died. As much as he loved her, he didn't have the right to do that to her.
Suddenly, the console of the TARDIS took on a life of its own and began to move through time and space. She didn't do this often, but it wasn't everyday that a TARDIS got to make both her thief and her companion happy at once. Where she was taking them was somebody who could make their wishes come true.
When the TARDIS finally landed, the Doctor tentatively looked out the doors to see a barren moonscape with no one in sight. Lauren finally joined him outside the TARDIS and took in the stars above them.
"Welcome, Time Lord," a voice said. The Doctor and Lauren looked to see an old man who hadn't been there before standing in front of them. He was a bit taller than the Doctor, and he looked as old as the Time Lord really was. "I am the last of the Great Old Ones, and I am dying."
"Great Old Ones?" Lauren asked.
"The Great Old Ones are ancient beings that shouldn't really even exist. They were in Time Lord fairy tales, I thought they were just fabrications to help inspire Gallifreyan children but apparently I was wrong."
"Yes you were, Doctor. I have quite a bit of power to give, but not much time to give it. I sent a call out to your TARDIS and she brought you here to me so that I might grant the desire of your hearts, Doctor."
The Doctor didn't know what to say at first. "You mean... you can bring the Time Lords back?"
The Great Old One shook his head. "No, I do not have that much power, Doctor. But there is something that you do want that you won't even admit is the desire of your hearts." The Doctor immediately knew what he was talking about.
[No,] the Doctor shouted in Gallifreyan. [I don't have that right. I can't do that to her. If she were to become a Time Lady, she would outlive her family by thousands of years. It's bad enough that I have to do that to people who I know for only short periods of time, to her, the pain would be excruciating!] Lauren was confused. The TARDIS normally translated alien languages, but for some reason, she couldn't understand what the Doctor was saying to the Great Old One.
[Then who has that right?] he countered. [Who but you can have that right. You have lost more things than any one person stands any right to lose in ten lifetimes, all in for the sake of the universe, and now that the universe is finally willing to pay you back for all of that, you refuse its gift?]
The Doctor was so mad at what the Great Old One said that he shouted in English, forgetting momentarily to speak in Gallifreyan. "Do you think I want to refuse what you're offering me? I love her, but I'm not willing to make her stand by and lose her family to death while she stands by ageless because I was selfish and wanted her for a wife!"
Lauren couldn't believe what she was hearing. The Doctor loved her? It seemed so ridiculous, but didn't she love him too? It had taken her a while to admit it to herself, but the way that he conducted himself was just so different that she couldn't help but fall in love with him. His views on life held such wisdom and passion that she had never seen in anyone, and she loved it.
"You love me?" she asked quietly. It was only then that the Doctor realized he had responded in English. Turning to Lauren, he answered, "Yes, Lauren. I do love you, but don't you see? I can't love you. I'm a Time Lord, and it's my curse to not be able to love anyone because everyone that I get close to dies. What the Great Old One is offering is a chance to turn you into a Time Lady which would take that away, but then you would have to stand and watch as your family ages, withers, and dies while you just regenerate.
"And the day will come, Lauren, when even I will die and you will live on. This is my twelfth face, I've only got one more left before I die, and I just can't make that decision."
"If I could get a word in," the Great Old One said. "I can not only make her a Time Lady, Doctor, I can also give you an extra dozen regenerations. You and your love can live a life together."
The Doctor stepped closer until he was within inches of the Great Old One's face, spitting his words out with the fire that is the Time Lord. "I. Will. Not. Make. Her. A. Time. Lady."
"You don't have to make me one, Doctor." The Doctor turned, and saw that Lauren had a very determined look on her face and her hands set on her hips. "Two days ago was my eighteenth birthday, which on earth means that I'm an adult, and capable of making my own decisions. If I want to become a Time Lady, then that's what I'll do."
The Doctor looked intently at Lauren and spoke as calmly as he could. "Lauren, I want you to think about the decision you're about to make here. You're choosing me over your family. Are you really willing to travel with me for hundreds of years instead of having a life with them?"
Lauren thought the Doctor's words carefully. It was true that she would have to lose her family eventually, but she really did love the Doctor, and wanted to be with him. She wanted to be his companion through all of time and space, and was willing to make the sacrifice to do so.
She slowly nodded her head. "Yes. I love you, Doctor, and I want to be with you forever, if you'll let me."
The Doctor nodded his head as well. "Then do it, Old One. I give you my permission."
The Great Old One merely waved his hand at the two of them, and the Doctor felt a new vitality enter into his body as the extra regenerations were added to his genetic code. But Lauren was not so fortunate.
She cried out in agony as a fire burned through her entire body and her cells were transformed at the genetic level. Her one heart became two, her body temperature lowered, and many other changes occurred inside her as she changed from a mere anthrozil into an adopted Child of Gallifrey. When the process was complete, she fell into the Doctor's arms.
"And with that," the Great Old One said, "I take my leave of this universe. But before I fade into nothing, allow me to wed you."
Still slightly weak, but feeling better by the minute, Lauren stood by the Doctor as the Great Old One married the Last of the Time Lords.
"Now, Doctor, you may kiss your bride." The Doctor turned, and pressed his lips to Lauren's, savoring their flavor on his own. They only parted when they needed to breath, but when the turned, the Great Old One had faded into nothing.
The two Gallifreyans walked arm in arm back to the TARDIS, which the Doctor promised he would teach Lauren how to fly someday. Unable to resist tradition, the Doctor hefted Lauren into his arms and carried her over the TARDIS threshold before setting her down in the bedroom that they would now share.
Unable to contain herself, the TARDIS flipped her own dematerialization lever, allowing her thief and his love to relish in the birth of a Time Lady.