There stand two beings in the aftermath of a scene of chaos. For the purposes of simplicity, since we are only feeble-minded humans, let us call them both men.
The first "man" is formless and beyond comprehension, even by the minds of gods. He is old beyond imagining, old as the very concept of life. Let us pretend he is a human, and that he is gaunt, with black hair, pale skin, and the formal suit of an undertaker. He is perhaps fifty years old in appearance, with a look of polite tolerance on his face. His cane is decorative, and sometimes clacks against the plain silver ring on his finger.
The second "man" is so very similar, and yet opposite. He, too, is old, though nothing more than a child in the gaunt man's eyes. He is, in some ways, difficult to comprehend. Yet he is not formless, not by far. Truthfully, he has too many forms: old and young, large and small, male and female. He has one with red hair he is particularly fond of, though perhaps more due to novelty than anything else(he is quite a fan of novelty). Each form is somehow familiar, like that of an old friend, though they all wear unusual clothing. Yet his eyes never change. Not in the way that matters. They never lose that look that says, "nobody should ever lose what I have lost."
"It's a pleasure to finally meet you, Doctor" says the first man mildly. "I've seen you so many times, I sometimes forget we've never talked."
"I'm sorry," interrupts the Doctor, in a characteristic rapid speech, "who are you?"
The Doctor looks around, his eyes scanning the quieted chaos as if wondering where everyone went. He takes in all the incomprehensible details of the other man, and all of the horrific scene around them. Before the suited man can reply, he pieces it together.
Normally, he would go on about how he came to his conclusion. Even half an hour previously, he might have. There was always somebody who couldn't quite keep up, so he would give some rapid-fire explanation and get on with whatever he'd been doing. Usually running.
"I'm dead," he concludes without any ado. He has nobody to explain himself to. He never will again.
The ancient man nods, still with that look of polite tolerance on his face. He watches the Doctor kneeling on the ground, brushing incorporeal hands on a fragment of plaque that reads "assist" and "imm".
Then the man stands. The sorrow slowly drains from his ever-shifting face as he refocuses his mind.
"And you are…?" A light seems to go off in the Doctor's head, and he rattles off, "Grim Reaper? Time Wraith? Personification of the Foundation? Living psychic construct?"
"Death," Death answered mildly.
"Death itself," asks the Doctor, skeptical but fascinated. "That would make you a discrete part of the whole, come to collect me, or perhaps a psychic image? No, no, I'd know the feeling. Maybe -"
"There is only one of me," Death interrupts with a tolerant nod, "though I have quite a lot of help. I don't often visit personally."
"Oh," says the Doctor more quietly, rather put off by having his train of thought interrupted. "You've seen me before, but we haven't met… oh. Oh dear."
"I thought I'd make an exception," Death gives a small smile. "There aren't many beings I see more than once. None I've seen as many times as you."
A nostalgic look comes over what passed for Death's face before he tilted his head. "Perhaps one, a long time ago."
"Even so," asks the Doctor leadingly, looking around, "isn't there something more important going on?"
"All in good time," Death assures him, turning to walk through the carnage. "You've made my existence interesting, and not many manage that. I'd like to enjoy the moment. I must say I was a bit frustrated with the first time… Time… reset itself. It was quite the trick. And I've been around long enough to see a few."
The ever-shifting man has the dignity to look embarrassed. "It was -"
"An accident," Death interrupts with a hint of acerbic doubt, "like what happened to your home? You hid an entire planet from me, Doctor, and that is not something done lightly.
"Of course," continues the ageless entity more calmly, "that pales in comparison to what you've just accomplished."
Every one of the Doctor's ever-changing faces takes on a look of profound wonder. "You mean it worked?"
A weight seems to lift from the Time Lord's shoulders. For the first time in a long time, something extra shines in his eyes.
Death nods. "I thought you'd want to see," he says with a congratulatory tilt of his head. "It is, after all, a remarkable achievement. I can understand wanting to know the ending."
Suddenly, the two beings are far from where they were, far from the planet that had briefly become the most important place in the universe. The planet on which the maddest of plans had miraculously succeeded. They stand just outside the edge of the universe, watching the very last stars go out.
"It's beautiful," the Doctor whispers. "Even now, it's beautiful, isn't it?"
Death nods again and gives a true, full smile. "It is," he agrees. "I'll tell you a secret, Doctor. I suppose you might understand, oddly enough."
As the universe, what is left of it, flashes wildly, Death speaks over the soundless roar of… himself, "I dislike my job. Very much."
One could say that Death grows in that moment, but in truth he is infinite. The universe is a toy to him, he who has reaped even Gods in the eons before now. Holding out his hand, he encloses the fading, roaring light of the universe. Beneath that great hand, there is no bang or whimper, but the incandescent sound of a deafening brilliance, reduced to embers in an instant.
Small again, holding what is left in his hands, Death admires the mote of light.
"Remarkable," he breaths.
Then he holds it out to the Doctor, splaying his hands wide to reveal the softly glowing, yet infinitely bright light of what was once the universe.
"I believe you deserve the honours," Death says solemnly.
Taking the speck of the universe from Death itself, the Doctor holds it in hands held wide, and he weeps.
Then he lets out a great rush of breath.
And breaths life into a new universe.
Death takes his hand and pulls him away.
"I want to see it," the Doctor says, pulling away, but Death shakes his head and holds tight, smiling mysteriously.
"There are some people waiting who want to see you more."