I have taken great liberty with the Laws of Time and never saw any episodes with the character on whom the gimmick turns -- never even mind the whole ethical conundrum. But they did it in X-Men III, so it must be okay. ;)

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The Nature of the Beast

She shone all the brighter in the depths of Krok-Tor, piercing its ruddy darkness with a light pure and beautiful. Joy welled up in the Doctor's heart as never before, for she was the answer to everything; she'd given him Rose, she'd given him victory, and she'd given him back his life.

The doors opened and closed, and the TARDIS shone even brighter; then she faded, deserting the dying cave. Stones, boulders, slabs of rock pounded out of the endless hole, cutting it off entirely from the cavern within. Gravity had claimed the dead planetoid for its own, and the black hole was tearing it apart.

Then, two feet to the right of its original position, the TARDIS reappeared.

Out popped the Doctor, one arm tangled in a mess of technology, dragging Rose after him by the sleeve of her jumper. The girl, minty-fresh and opaquely mascaraed, was not very surprised to observe that the ceiling was raining down around them as he pulled her along the tunnel. "Were you planning on telling me what we're doing here?" she shouted at the Doctor's unheeding back -- and then they reached the mouth of the cave, and something primal clawed its way out of the back of her brain, and she didn't even hear herself screaming.

The cavern opened out before them, miles deep and miles wide, and the space was almost entirely taken up by the Beast. Massive, terrible, wrenching at the shackles that bound it to the wall: it leaked fire at every joint, and the horned head shook in pain as gravity found a foothold in its enormous body.

"There you are, you beautiful thing!" cried the Doctor, unloading a wiry technical tangle on one of the empty plinths. "Didn't expect to see me again, eh? This is Rose, you wouldn't have met her before, she's up there in the ship right now in fact, don't mind the noise, we're just breaking you out--"

"What!?" Terror lent power to the girl's panicked yell: it cut even through the frantic bellows of the Beast. "I know what this is. This is that thing, isn't it? The sin and the temptation and the pain and all the rest? 'Cos nothing else could look like that!" She clung to the Doctor's arm, remembering the creature's dark snarl throbbing through her skull -- knowing things she'd never told anyone, foretelling her very doom. "This is the embodiment of evil since the beginning of the universe, and it's about to fall into the black hole and be safe and gone--" she ended on a shriek -- "and you're about to let it go?"

"Well," said the Doctor, "not exactly, not as such, no, I'm not going to let it go." He waved a free hand at the creature, nearly losing it as a flame shot a bit too close. "Just this."

"Well, call me stupid, but I don't see the difference!"

"Stupid, isn't it obvious?" Still pointing at the Beast, he tossed her a circuit board. "Over there where the other urn was, will you? You can see it a mile away. Look at it. Look at its eyes."

Rose looked up at the Beast, her breath stilled with sheer horror. It had been bad enough, sitting in the rocket with Toby raving about blood and terror and evil and mastery, but he'd been human, sort of, at least to start off with. Even as his eyes shone red and his mouth spat fire and the ancient script wrote itself over his skin, he was only human, a terrible intelligence in too fragile a shell.

Flames wrapped around the Beast. The horrible mouth gaped and it roared again. The eyes flared -- yellow, this time -- with mindless, animal panic.

"Had to break a zillion laws of time, but who cares about those anymore? Besides, it's so gonna be worth it." Grinning like the maniac he was, the Doctor threw the switch.

Time twisted. And they were somewhere else.

(O.o)

The Eye of Orion was slightly cold, smelling of geraniums, butter drops, and a hint of brimstone. A mild breeze, agitated by the presence of a new heat source, batted at their faces like clumsy paws. The Doctor and Rose opened their eyes simultaneously, saw the Beast, and screamed.

It screamed as well, though the construction of its vocal apparatus turned the sound into something more reminiscent of a menacing howl.

"AAAAAAGH!" yelled the Doctor and Rose again, stumbling backwards and landing in an ignominious cloud of dandelion fluff.

A few yards away, the Beast climbed to its knees, surrounded by a circle of smouldering ground cover. It was even bigger up close: rangy, roped with slick sinews, ghoulish, horrific, and totally evil. The new intelligence behind the burning eyes should have made it all the more frightening. Instead, it seemed confused.

"What..." Its voice was like an avalanche. "I was..."

"There's bound to be a moment of disorientation," muttered the Doctor in Rose's ear. "Like waking up as a giant jelly baby, only a bit less gooey. And somewhat larger. And more able to do something about it."

"Shouldn't we be running, then? Before it sees us?"

"Too late." Switching on his patented mad grin, he bounded to his feet and waved. "Oi! Down here!"

Clearly sanity was not on the menu today. Rose, deciding that she could at least die comfortably, flopped backwards into the weeds.

The Beast swiveled, its shoulders hunched. The yellow eyes, pale under the clear sunlight, narrowed suspiciously.

"Oh, look at you," said the Doctor, standing on his toes, practically vibrating with delight. "How do you feel? Nod for yes, that's it, get those motor skills under control. Intellect settling in well? Remember the last moment of your life? I always want to ask people if they remember anything more than that, but you can never get ahold of them after they're dead..."

"What am I? What have you done?"

"Okay. Short version?" The Doctor stabbed a finger up at the Beast. "You died. In the meantime I -- it's me, the Doctor, by the way, yes I've regenerated again but let's not talk about that -- discovered a pan-dimensional demon creature whose evil mind had been separated from its body. Destroyed the mind, carted the shell back here, and in a fit of absolute genius managed to recover your mind and plant it in this new and only slightly disused body. Fantastic, isn't it? Obviously loads more efficient than your old one--"

"Wait, wait." Rose was used to the Doctor's normal grandstanding, but this was a bit much. "Now you're trying to bring someone back from the dead!?"

He brushed the question aside; his waving arm nearly hit her in the face. "'Course not."

"I mean, wouldn't that be satanic or something?"

"--I already did it," sang the Doctor. "And he's not satanic anymore on account of this is someone else. An associate from the afterlife, a guest from beyond the grave..." He rubbed his hands gleefully. "And I hope you have a lot to say about it, 'cos oooooh, I have questions."

If it weren't for the teeth, the Beast's dangling jaw might actually have looked comical.

After a moment, it shifted, settling its massive lower limbs. Heat waves rolled over them; another foot or so of dandelions went up in flames. Hunched over, the rough knuckles of one hand digging into the ground, it gave an overwhelming impression of leashed motion. Rose couldn't shake the feeling that it was poised to spring.

It spoke. The weight of its attention bore down on them like the fall of a civilization.

"You think you know me?"

"Adric of Alzarius," said the Doctor proudly, flinging his arms wide in welcome. "Rose, Adric; Adric, Rose Tyler of Earth--"

"Not likely."

"What?"

Its ragged lip curled up. Flame leapt in its fathomless eyes.

"Oh." With lightning reflexes, the Doctor whipped out his sonic screwdriver. His voice went all rusty. "Well, you can just get back then. D'you think I opened up that path for anyone at all to slip through it?"

The Beast leaned in close. "Make me."

The Doctor looked at the Beast, then at the little glowing light at the end of the sonic screwdriver. Up, down, up. He opened his mouth to speak, closed it, glanced at Rose, remembered to breathe, turned back to the Beast and forgot again.

"Didn't think of this, did you?" The dark snarl rolled over them, roiling the clean atmosphere with the creature's unholy glee. "And you had such plans. Life from death? Redemption from your sins? Poor altruistic Doctor, always falling for the most obvious path..."

"Who are you?" the Doctor whispered.

It smiled. The effect was positively devilish.

"Do you know how intensely I've longed for this, Doctor? How I've dreamed of this moment? And now you've brought me back to life and given me this magnificent new body... imagine the worlds I could dominate, the destruction I could wreak, all thanks to you..."

It laughed. The sound reached right down into the nerve centers and flayed them alive. Rose shuddered all over.

"Who are you?" snarled the Doctor. Domineering. Meglomaniacal. It could be any of a thousand dead foes. Davros, Omega, Sutek, even the Master -- oh, lord, it would be him, wouldn't it? Wasn't it always?

"I could kill you right now, Doctor--"

"Oi, get in the queue," said Rose shakily.

This was familiar ground. Pulling himself back together, the Doctor met the Beast's eye challengingly. "You won't, though. I know your type. Snuff me like a candle, standing here defenseless in front of you, oh no, that'd be far too easy. You want a bit of challenge -- a run for your money, eh? Universal blackjack, winner take all?"

"No," said the Beast. "That would be stupid. Why would anyone take a risk like that when they could simply squash you now and save the trouble later?"

The Doctor deflated. "Oh."

"You're lucky," said the Beast calmly, "that I did turn out to be Adric. I mean, imagine whom you could have ended up with?"

Dead silence. Then the Doctor, in a somewhat strangled tone, squeaked, "Adric?"

"I was right, you know, Doctor," said the Beast. "If not for that Cyberman--"

"Adric?" repeated the Doctor, one decible higher.

Rose considered whacking him in the head, but that would entail getting up. The Beast just sat there.

"D'you know," said the Doctor, "I'd forgotten how annoying you were?"

"I can still squash you, Doctor."

"But you won't." The Doctor shook his head, smiling fondly up at the enormous monster. "'Cos you're Adric. Good old Adric, always in the right, never a simple solution when a complicated one would do the trick, all that maths and not a single Earth reference. You know, I missed you, Adric. For a good long time -- whoa, watch the hair, watch the hair!"

He cringed as the enormous hand came down, then stopped in astonishment as the flames withdrew up to its wrist and the creature patted him carefully on the head.

The Doctor grinned. Reaching up, he high-fived the Beast's right thumb. It felt like flash-heated sandpaper. The giant face grinned back, and the Doctor made a mental note to have a word with poor Adric about his teeth.

"I think your little friend's fainted."

"She'll just have to get used to it. Come on, old friend. Let's do some good."

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