Davros gloated. If he had a heart, it would have been brimming over with the joy of revenge; as it was the mechanical device that had replaced that organ ran faster.

His greatest enemy, the Doctor, was helpless before him. His companions as well, just as Dalek Caan has predicted: even Sarah Jane Smith. She had been there for the beginning; it was only fitting that she attend on the Daleks' greatest victory. The TARDIS had been destroyed, and more: the Doctor's faith had been crushed as well, as Davros revealed to him the black consequences of his own manipulations.

Outside his Crucible (he thought of the spacecraft as his, even as one tiny analytical portion of his mind noted that he was not its current master; that it was a Dalek ship, and Davros was present only to guide them), twenty-seven kidnapped planets hung in unnatural alignment, to channel the energies of the Reality Bomb and obliterate the universe.

The intercom crackled, "Countdown to commence in...in...in..." The Supreme Dalek's mechanical voice stuttered, then firmed. "Intruder alert. Intruder alert! Activate ... defences ... rrrrr..."

The Doctor quickly tried to think of Things That Would Make The Supreme Dalek Go Rrrrr, and none of the possibilities he came up with were good.

"What? You must start the countdown! Obey me!" Davros shrieked, and his shriek was met with the sound of tearing metal. He turned his eyeless face to the side of the Vault, and the prisoners did as well.

There was something there. Four somethings; four bars of light that seemed to be stuck through the metal wall, like straws piercing a fruit rind. The Doctor had the distinct sensation that the four bars were somehow solider than the wall, harder or realer or ... something.

Then they moved. They cut, four bars of light, white and red and fire-edged black and a fluttering iridescence that combined all three colours; they cut, each moving away from the other, and leaving behind a like-coloured line through which an uncanny white light burned. The bars were moving to form a square now, and the Doctor just had time to register that they were not bars, but some sort of blades, when the cuts in the wall formed a great square which toppled backwards into - nothingness.

But it wasn't nothingness. It was a glowing brightness that seemed to bleed into the darkened room. A strangely complicated light, with flickers of all colours in it, that was blotted out for a moment as a slim figure stepped through.

The Doctor's fascinated gaze was wrenched aside by a movement seen out of the corner of his eye. Davros was obvious taking the position that retreat was the better part of valour, wheeling himself backwards into the shadows. Strange, that all the Daleks were doing the same. There was no noise from the Supreme Dalek over the intercom, only low rasps and creaks that might be the sounds of metal on metal, or of a being driven speechless by fear.

The figure came forward, and was revealed as a man. A man of medium height, with white hair and dark crackling eyes, and a white suit with a distinctly scientific air to it.

"Who is that?" Rose wondered aloud, and flinched as the dark eyes turned to her. Those eyes were - depthless, changing, blurring colours of brown and black and hazel merging and combining; eyes like a boiling sun of darkness.

Beside her, the Doctor smiled. Smiled so wide that his jaw ached. He had never hoped for this but...here he was.

"That, Rose, is proof that even Davros can bite off more than he can chew," the Doctor breathed. "That is the White Guardian."

"The White Guardian?" she asked.

"It must be. One of the Eternals; beings of almost limitless power. I thought they had fled the Time War, but-"

The Guardian paced closer. His quick gaze leaped around the room, seeming to absorb its every angle and contour in an instant, before returning to the prisoners before him.

"The Doctor, of course." The Guardian's voice was a little lighter than the ominous eyes might suggest, with an ironic tinge to it. He paused for a moment, looking the other man up and down. "You know, every time I see you, you've done something even more dreadful to your hair."

"To - to my hair?" the Doctor stuttered. He reached up to try and mash down his flyaway strands.

"Yes, this is even worse than the curls. But perhaps you can help me, Doctor." The Guardian came closer and smiled, friendly little lines forming around his mouth as he did so. "You see, someone or something has been punching holes in the walls between the dimensions."

"Oh. Oh, really?" the Doctor said, trapped. He knew much too keenly that the person who had done some of that punching was currently standing to his left, but telling the Guardian this little fact did not seem like the best plan.

"Very unstable holes," the Guardian said, a touch of menace now creeping into his voice. "Holes that take considerable energy to find and to repair. And there is also the matter of a large quantity of sentient beings that have somehow been dumped into the Howling between. You might say: why does this concern someone from eternity? Well, true, I do not live in reality, but I do enjoy visiting it. And I am not interested in seeing it randomly destroyed, or the barriers that keep it whole corrupted."

In the shadows, Davros' metal fingers flicked again and again at his control panel, urgently trying to summon the Daleks to do battle with the intruder. He had to be exterminated! The Reality Bomb had to be detonated! But even as his fingers moved faster and faster, unease grew somewhere deep in his mind. He had not seen the intruder's face, but his voice...he knew that voice.

"You." This was not addressed to the Doctor. A coloured shadow suddenly formed on each side of the Guardian; one was a billowing mass of infinitely subdivided black spines, shivering and rippling, hovering like a crawling plume of darkness at the Guardian's elbow; the other was a twining red mist whose fine strands looped and coiled around themselves. Both of these - things - felt powerfully alive to the Doctor, but he had no idea what they were.

"Search," the Guardian ordered. The two shadows rippled away, and the Guardian turned on his heel again, examining the prisoners.

They were rising to their feet; Jack in particular was looking rather wide-eyed at the realisation of just what sort of being they faced. Mickey and Jackie just looked confused, Martha was cold and determined as ever, and Sarah Jane looked on the point of snapping.

"An interesting lot of companions, Doctor," the Guardian finally said. Then his attention was drawn to the massive bank of controls that dominated the room, and he went to it, running his hands over the knobs and metal keys with easy familiarity. He leaned forward and seemed to slip his face into the machine, passing through the metal like it was a ghost.

Jack immediately tucked his head back and stopped moving towards the stranger to introduce himself; his experience had taught him to always keep at least an arms-length away from beings that could phase through matter. You never knew when they would reach inside you and start stirring things up.

The Guardian straightened, and a truly ferocious frown took over his face.

"This is linked to a matter destruction bomb," he said, every word bitten off. "And it has trans-dimensional capabilities. With the proper foci, it could destroy all of every reality!"

"No." That from Davros, who suddenly emerged from the shadows, his support chair gliding forward bearing his withered body. His voice shook with emotion: hatred smothering up fear. "No, that is not your face. That cannot be your face!"

The Doctor's eyes darted between the two not-men, monster and Eternal, wondering if they would attack each other on the spot. Mickey looked like he might be rooting for that to happen.

"Well now!" The Guardian looked down at Davros with an expression of amused benevolence. "So, it's you. That explains much."

"You have not explained why you are wearing that face!" Davros snapped. His fingers had stopped picking at his controls; instead his hand waited on the instrument board, a little poised, as though it could somehow strike.

"No? Well, perhaps I could tell you a little story." The Guardian smiled, his teeth shining as white as his clothing and hair.

Far above this conversation, the Supreme Dalek sat alone and quivered, and listened. The other Daleks were spiralling irregularly around the floor before it, helpless in the great flood of data and information that was pouring into their deepest, most central circuitry and chemical programming. What was down in the Vault was overwhelming and terrifying and horrible and wonderful, and the Daleks who had not already fled into space listened as the one called the Guardian spoke.

"Once upon a time - isn't that a nice way to start a story? Well, once upon a time, there was a scientist named - Davros. He was born in a bad time, during a mad war, and it's no secret that he was mad and bad as well."

Davros seemed to sink in his chair. "Continue," he growled, enduring the insult. The longer the intruder kept speaking, the more chances for the Daleks to come to their senses and attack.

"He was a scientist, the greatest scientist of all time." The Guardian's eyes grew misty for a moment. "He saw the future of his war-ravaged planet: saw that Skaro would soon become a wasteland inhabited only by the mutated fragments of his race. And he planned to take control of those fragments; brainwash and enslave them, install them in carrier machines of incredible power, and use them to end the war and rule his planet." The Guardian smiled thinly. "And he succeeded. More: he found a way to transfer his intelligence, his mind, out of a body that had nearly been destroyed in an enemy attack, into a new and healthy body."

"What?" the Doctor and Davros said as one.

"And it was after this transfer that Davros started to have the most incredibly annoying troubles with…time travellers."

The Doctor's lips curled back in a flinch.

"What do you mean, troubles? I remember-" but Davros was interrupted by a wave of the Guardian's hand.

"Oh, all sorts of troubles. Some people came to assassinate him, some came to join him, some came to hire him - to hire him! Imagine that!" The Guardian bristled with indignation. "To hire the greatest scientist in the Universe: to try and buy the priceless labours of his matchless mind with money." He repeated the word with a weight of awesome contempt on it. "Money."

"But Davros noticed something about these time travellers. They were looking for him as he had been: a cripple confined to a support chair. He deduced that these time travellers were coming from alternative futures - or pasts. That they were looking for the man in the chair, not Davros as he was now. So - he cloned himself."

"He cloned himself." Davros' voice was flat.

"And then he took that clone," the Guardian leaned close, and his voice grew softer, "and he artificially aged it. And he burnt it, scarred it, maimed it, smashed and crushed and tore-"

"No," Davros breathed, but the Guardian's voice rolled on relentlessly.

"He destroyed that clone and yet kept it alive, barely alive! Alive in his own support chair, implanted with a suitably edited version of his own memories and a slightly retarded intellect."

"Retarded?" Davros said, his voice going from his usual mechanical rasp to almost a squeak.

"He wanted a decoy, not competition." The Guardian stood very straight now, and he seemed to gloat at Davros' obvious distress. "And then he set the clone to work in his own Bunker, and before you know it, poof!"

"Poof?" Rose wondered, and glanced at the Doctor's face; the grief and fear she saw there froze her down to the bottom of her heart.

"Poof, it was gone! Abducted by time travellers! They dragged it away, leaving the real Davros free and undisturbed to continue with his work. Great works."

The Guardian tilted his head and smiled. "And so that's the story of why you are not Davros. You are instead a replica, a fragment, a copy of the real thing - how else to explain how you could be thwarted again and again by one mere rebellious infant, this Time Lord?" He gestured to the Doctor.

"You are not Davros. You are at best half of him. If that. Perhaps we could call you Dav."

"And then what happened to the real Davros?" the Doctor said, his voice flat with futility.

"He is here," the man in white smiled, glowing. "I am Davros. Davros, the Eternal."