"What is a Sigmarax?" Rose asked as tears formed in her eyes.

"A Sigmarax is an alien that's been around almost as long as the Earth has." The Doctor said. "It's basically a ghost, an invisible ghost, with the ability to change into whatever it chooses."

"Why is it taking over my body, then?"

"It needs energy to change into certain forms. It had enough energy to turn into something as simple as a necklace," he pointed to Rose's locket, "but they need more energy to turn into something bigger, like a deadly monster."

Rose's eyes widened. "So it's going to kill me?"

"Not exactly." The Doctor stood up and leaned on the console, trying to figure out what to do. He turned to Rose again. "It's like an unborn baby: it uses some of your energy and blood to keep itself alive, until it's ready. Then, it will go in for the kill." He patted the console.

"It wants the energy in the TARDIS?" Rose sat up.

"Yes. That's why it's in you. You live here, and it saw your memories of ripping open the TARDIS' heart, and absorb the energy, and it wants you to do it again."

"But... But… I can't. You know I can't." Rose said desperately.

"I know. But it's going to find another way."

As if it was on cue, the dark look returned in Rose's eyes. "Cardiff." She said darkly.

"Oh, Cardiff? What do you want to do there?" He said casually, pressing a few buttons on the console.

"Her memories indicate that there is a wormhole there. Plenty of energy…"

"Oh, so you can change from a measly little necklace into something that can actually do some damage?"

"I can kill the girl if I wanted to. But I still need her."

The Doctor reached into his pocket and pulled out his sonic screwdriver. He held it up to his mouth, and whispered, "Please don't kill her." He pointed it at Rose's forehead, and pressed the button.

Her eyes flickered back to life. The Doctor sighed in relief. "What did you do?" Rose asked.

"It's unconscious at the moment. Until it wakes up, I need to figure out what to do."

"It knows about Cardiff." Rose said nervously.

"I know." He crossed his arms and started to think. "First, we need to get it off of you."

"How are you going to do that?"

"Don't know." He said quietly.

"Can't you use your screwdriver?" Rose asked.

"It's fused too close to your heart. I don't want to do any damage." He said, still thinking. He then jumped up. "I'm full of energy, aren't I?" He jumped up and down at the console.

Rose realized what he meant. "No, you aren't risking your life just to get this think off of me."

"I can channel it away from me so it won't affect my mind." He walked over to Rose. "I can turn it into whatever I want if I try hard enough."

Rose stared at him. He sat down next to her. "I have to do this." He said. "I don't want to scare you, so…" He put his hand over her eyes. Before she knew what was going on, his lips were on hers. He kissed her lightly, but they both knew they wished it would last longer. As he pulled away and lifted his hand off of her eyes, they watched as the locket slowly disappeared. Rose pressed her hand against her chest as the hole the locket made disappeared.

As it completely dissolved in the air, the Doctor began to twitch. A metal brace formed on his wrist.

"Oh no you don't!" He yelled. He grimaced, and the brace disappeared. An apple materialized in his hand a few seconds later.

He dropped the apple on the floor and quickly shook off his overcoat and wrapped the apple in it. He picked it up and held it in his arms.

"Ah, there we go!" He smiled. "Now I just need to figure out what to do with it."

"Can't you just kill it?" Rose asked.

"If it isn't necessary, then no." The Doctor said, unwrapping the apple and holding it up to his ear. He then put it back in the overcoat, and said, "Its intentions are to get fuel for its planet."

"Fuel? Why is it on me if it wants fuel?"

"It needs to be something big enough to suck the oil out of the ground and bring it back to his planet."

"Oh yeah, those aren't bad intentions or anything." Rose crossed her arms. "What are you going to do with it?"

He placed the apple on the chair, and it disappeared. He examined the air and held his screwdriver in the air, pressing the button. He pulled it through the air and back onto the chair. It materialized into a pen.

"It's going to die." The Doctor said, kneeling down and examining it. He picked it up again and held it to his ear. "Hmm. Its planet doesn't need fuel."

"What does it need, then?" Rose asked, kneeling next to the Doctor.

"It's embarrassed." He turned to Rose. "He's looking for a mate."

He continued after seeing Rose's confused face. "It lied. Its planet does not need fuel. In fact, there are plenty of fuel resources on the planet it lives on. It's just lonely."

Rose looked back up at the Doctor. "Lonely?"

"Apparently, a lot of other Sigmaraxes are very superficial, and this one doesn't have enough energy to turn into something very likeable." He said. The pen twitched again. The Doctor pulled his screwdriver out again and pointed it at the pen, pressing the button. It materialized into a large cardboard box.

"Hold on a minute." He said, pressing the button again. It disappeared, then reappeared, taking on the appearance of a seven-year-old girl.

Rose stared at the girl for a few seconds. "It… it looks like me when I was a girl."

The Doctor smiled. "It must have traces of your DNA flowing through its system."

It walked up to the Doctor and tugged on his sleeve. "Change me again, please."

"Please? It's being all polite now?" Rose said, astonished.

"Like I said, it has traces of your DNA in its system." The Doctor said. Rose blushed.

He pressed the button on his screwdriver again, and the girl disappeared. It materialized into a young blonde woman, about the same age as Rose. She was tall, slim, and wearing a short black dress. Rose cringed as the Doctor examined the girl.

"Name me." The woman said. "Name me, Doctor."

The Doctor thought for a moment, tapping his chin with his screwdriver. "Romana."

The girl blinked, and Rose crossed her arms. "My name is now Romana." The girl said.

"Okay, Romana, are you going to return home now?" The Doctor asked sternly.

"Yes, Doctor." Romana said quietly. "This energy will not last for long, though."

"I know." The Doctor said. He pulled a small box out of his pocket and pointed his screwdriver at it, then handed it to Romana. "Take this when you're out. It'll last for a while."

Romana smiled. "Thank you, Doctor." She turned to Rose. "And thank you too, Rose."

Rose smiled politely, and Romana disappeared into thin air.

The Doctor placed his screwdriver back in his pocket and walked back up to the console, pressing some buttons. Rose walked up to him, and said, "Alright, two questions."

"One at a time, please." The Doctor interrupted.

Rose continued, "What did you give her?"

"Energy capsule. A tiny bit of the TARDIS' energy pressed into a capsule. Should last her a few months at the least."

"And who is Romana?"

The Doctor looked up. "That Sigmarax that just disappeared into thin air."

"Where did you get that name from?"

The Doctor sighed. "She was a friend of mine. A friend from Gallifrey."

Rose's expression softened. "Oh." She said quietly.

"Well, she's gone now, so it doesn't really matter." The Doctor said, flipping a switch on the console.

Rose linked her arm through his. "I'm here, at least."

The Doctor smiled. "Yes, you are. Now, where to next?"

"Surprise me!"

The Doctor smiled as he flicked another switch, and the TARDIS went zipping through the time vortex.

Author's Note: That's it! I hope I did pretty well with it. That may have been a stupid name for an alien, and a pretty simple idea for one too, but I did my best. I plan to start writing another fanfiction in the near future, if you're interested. Thank you for reading, and please tell me what you think in the reviews!

I do not own Doctor Who. All rights for Doctor Who belong to BBC, NOT ME.