Regeneration
The Doctor stared at his companion who was still shaky from the ordeal of her regeneration. "I'm going to guess that this is the first time for you," he said with a smile.
"As a matter of fact, it is!" the woman, now in the form a small child yelled back with a lisp. "Don't you dare make fun of me either!" she added.
"I wouldn't think of it," The Doctor replied.
He walked past where the girl was still trying to get to her feet, and stopped in front of the control panel of the Tardis. He started adjusting various controls and bent down to look into a binocular view port. "It seems that there is another Tardis out there besides mine, also locked onto your distress signal," the Doctor said. "I wonder who that could be?"
The girl wobbled on her feet, trying to run towards the Tardis control panel where the Doctor was standing. She found that she was too short to reach the panel, however.
"Give me a boost up!" she demanded. "I need to look!"
The Doctor shrugged his shoulders and grabbed his companion about her waist to hold her face up to the view port. She looked to see what the Doctor has just observed.
"Acchonburike!" she cried out. "We must get out of here, and quickly! He's returning for me!"
"Who is?" the Doctor asked in a voice that clearly lacked concern.
"The Master you fool!" she replied. "He's the one who sent me though that time vortex to die on this world."
"Interesting. It seems the Master didn't know that you still had that device on you," the Doctor laughed. "In summoning my Tardis to your aid, you've also summoned your enemy!"
"Your's too I would assume." the girl said.
"We've had our differences." The Doctor replied, shrugging his shoulders. "Well in any case I'm not going to be able to get us off of this rock before the Master arrives, the time circuits are completely drained and will take a little while to recharge. That's the effect of an emergency distress beacon on a Tardis, or didn't you know that. The good news is that the Master's Tardis will also be so disabled."
Barely meters away from the Doctor's Tardis, a marble Roman column materialized. Just as the Doctor's machine's chameleon circuit had become locked on the image of an old London police box, the Master's machine now always appeared in its current form.
The other Tardis landed on the edge of the safe zone. The moist ground wasn't as stable as where the Doctor's machine stood, as the heat from the still molten rock next to it caused the ground to shift under the weight of the Master's machine.
The Master opened the door to his Tardis just as ground gave way. The Roman column tipped over and spilled the Time Lord out, he landed on top of the molten lava.
The Doctor had been watching the Master's arrival. Upon seeing his rival's predicament he ran towards the door of the Tardis, grabbing the gas mask from where it lay on the floor.
"Don't do it Doctor!" his companion cried out. "He's evil and you'll die outside from the poisonous atmosphere."
The Doctor ignored the girls warning and he rushed across the moist ground. He grabbed the Master by his boots, and pulled him to the safety of the Tardis. Once inside he quickly shut the door, and pulled off the gas mask.
"You're right," The Doctor coughed, "The air outside is rather foul, and that gas mask didn't have very much left in it."
The Doctor and his companion gazed down at the form of the Master. His clothing was burned away where he had fallen onto the molten ground, and his breathing was shallow. The Doctor pulled his sonic screwdriver from his coat pocket and used it like a medical scanner to diagnose a patient.
"His lungs are badly burned from his brief exposure to the toxic atmosphere. His burns are also quite bad, I wouldn't be surprised if he undergoes spontaneous regeneration right before our eyes."
The Doctor's words proved to be prophetic as the Master's form began to glow as his body began the regeneration process in an effort to save itself.
The two standing Time Lords watched as the Master slowly took new form. The glow surrounding him grew faint and he stirred.
The Time Lord that had been the Master stood up. He was now dressed in similar garb as the Doctor, he had a blue shirt under his jacket, and wore a yellow scarf around his neck. His long hair was completely white in color and he had a patch over his left eye.
The young girl looked up at the new arrival and she kicked him in the right leg.
"Why did you do that to me?" the newly regenerated Time Lord asked in a soft voice.
"Because you're the Master!," She yelled at him.
"You've mistaken me for someone else," The Time Lord replied. "My name is now Kiriko."