Haha, it seems I wasn't the only one to think of this.
Nonetheless, I'll stick up what I've done so far for your entertainment/amusement/derision.
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Time of the Forsaken
A Tenth Doctor Tale
Chapter 1
=I=
The TARDIS shuddered violently, waking the Doctor with a start. He leapt out of the plush leather chair he'd been dozing in, leaning out of the door and gazing down the long, uniform corridor leading to the heart of the great machine. The shivering moan of metal under stress came echoing down from the other end, and he darted from the door of his latest study (they rarely lasted more than a few months before another room piqued his interest) and started to jog. The corridor shook again, the lethargic moan turning to a shriek as the lights briefly flickered above him, quickening the pace of his sneakers on the smooth metal until he reached the control room, the pulsing heart and mind of the immense vessel.
He tugged a screen down from it's cradle to face him, his frown illuminated by the red glow of insistent warning glyphs. “What's wrong, girl? You shouldn't be having this much turbulance, not out here..” The screens evidently disagreed, but their objections were cut short, the display flickering and starting to emit a low buzzing noise as the lights dimmed again. The Doctor felt the floor heave sideways beneath him, leaving him weightless for a moment before being slammed against a wall, his skull narrowly missing a bulkhead. He clawed his way back to his feet and staggered over to the control panel once more, throwing back levers and dialing improvised algorythms into the vast machine's nest of computing matrices, trying to compensate for the collossal forces buffeting the ship. Something had breached the surface of spacetime itself, and was throwing the TARDIS about on the jagged waves and eddies around it like a bath toy.
Rose came staggering out of an adjacent corridor, her hair and pyjamas indicating that she too had been awoken by the sudden impacts. “What's going on?!” she yelled, struggling to make herself heard over the din of straining alloys and shrieking klaxons.
“Something's breaking up the consistency of the space around us!” The Doctor replied, dialing a hurried string of digits into a keypad. “Hold on, we're going to have to ride it out!” He braced himself against the control panel, throwing a glance back at Rose, who had found a railing to cling onto. He gave the girl a nod, before throwing a large, black-tipped lever, sending the craft spiralling into the breach.
=I=
Rose awoke, her head a woollen mass of dull, red pain. A bright blue light was coasting lazily back and forth into her field of view, and she turned her head, reaching up with one hand to obscure it.
“Uh-uh, stay perfectly still. I need to finish this, or you'll end up with a concussion.” The Doctor was crouched over her, the blue light emenating from the sonic screwdriver held a few inches from her head. He was looking down his nose with an expression of intense concentration, and it took Rose a moment to notice the dried blood crusting on his brow like a coat of rust.
“I think you might need that more than I do.” she murmured, notheless staying still as he completed his work.
“Nah, I'm fine. I'm always fine.” He gave her a reassuring smile, and slipped the device back into his pocket. “Come on, a walk'll do you good.” The Doctor reached down, offering her his hand.
“Where are we going, exactly?” Rose took the offered limb, getting up unsteadily and walking across the floor, trying to work out if it was at an unusual angle, or if that was just her head.
“We've crash landed on a planet. Or, I assume it's a planet. The TARDIS' sensors are dead. It could be an asteroid, a spaceship, for all I know.”
“Shouldn't we wait for the sensors to come back online? Y'know, to make sure it's safe?”
The Doctor turned and gave her a reproachful grin, shrugging his shoulders. “Now, when've I ever done that, eh?” He threw back the doors of the TARDIS, and Rose flinched, closing her eyes instinctively. However, it wasn't the vacuum of space that greeted her. More the smell of.. Sewage? She wrinkled her nose, hurrying after the Doctor, who'd already stepped out onto the flatulent planet's surface.
The TARDIS was ankle-deep in what she could only assume was sewage, the Doctor having stepped up onto a concrete ledge that seemed to have exuded from the wall, coated in grime and moss. The sky was grey and dim, without a sight of what alien stars may lie above.
“Well, where are we, then?”
“No idea.”
“Is it safe?”
“Not a clue!”
“Then where are we going?”
The Doctor frowned, tapping his nose with his screwdriver, as if deep in thought. “That way!” He proclaimed, pointing down the open sewer towards the looming shadows of a city a short way off.
“Fine, so long as we don't have to walk through poo the whole way.” Rose grumbled, climbing up onto the ledge and following after him. They walked in silence for a while, listening to the sounds of their new environment. The water (if it could be called such by this point) was turgid and thick, gargling with a clogged lethargy beneath them, and the dim flourescent lights that hung in metal cages along the wall buzzed intermittently. The sounds of small feet scurrying through grates and up walls heralded the verminous inhabitants of the sewer noticing their appearance, and pretty soon the sounds became part of the overall background. Rose became bored, kicking at debris and trying to breath through her mouth.
“How long are we going to be down here?”
“Not long, look. An access route. Probably leads back up there.” He indicated what she supposed to be the ground level, about 20 feet above. She could make out the dark sillhouette of railings, but little else.
“Wonderful.”
They turned into the alcove he had pointed out, which sure enough lead to a set of stairs. The door to the stairway hung listlessly on it's hinges, the lock long rusted away and the steel door hanging ajar.
“Here, look at this.” The Doctor indicated a poster that had been attached to the other side of the door. It was shabby and mold-eaten, but Rose could still make out the imposing image of an approximately human figure, but made soley of blue metal, with a beaklike mouth and smouldering red eyes. He was pointing at the reader, and holding some sort of heavy rifle in his other hand. The heavy printed script read:
'Citizens: Defend Your Imperium! The alien, the mutant and the heretic want to lure you from the Emperor's light. Be ever vigilant! Tell your local Adeptus Arbites office of suspicious behavior in your family & neighbors.'
The Doctor leaned closer, inspecting the poster with care. He had taken out his glasses, perching them on his nose as he analysed the text. “Fascinating.. It looks like an amalgamation of.. There's German, a touch of English.. A heavy dose of Chinese in it's lineage, too. They're long in the past by the looks of things, though. This must have taken thousands of years to develop from it's root components.”
Rose sniffed. “You mean there are humans here? What about those things?”
“I think that's supposed to be an Arbite. Protector of some sort.”
Rose looked at him incredulously. “You mean there's a human under all that?”
The Doctor nodded. “Could be. Or a military android. Many cultures develop those, though more of them prefer not to put guns in the hands of their robots. Tends to disrupt the power balance a wee bit.”
Rose shivered, pulling her jacket closer around her. “Great. Paranoid robots with guns. And it seemed like such a lovely planet.”
The Doctor shrugged. “You've only seen the sewers. Let's go find out what the rest of it's like, eh?” He took to the stairs, climbing them two at a time. Rose sighed, following quickly after; nomatter the situation, the Doctor always seemed to brim with an irrepressable enthusiasm.
The top of the staircase brought them out on a long dirt road, bordered on both sides by waist-high walls of cement, long inhabited by generations of moulds and funghi, coating the polluted grey surface with mudded bursts of colour. There was graffiti too, but most of it was smudged into meaninglessness by age. The Doctor was already ahead of her, gazing over the opposite wall. She walked over to join him, and found herself gazing out at a huge, branching network of sewage canals, identical to the one the TARDIS had crash landed in. The Doctor let out a whistle, turning to her with a grin.
“Look at that. Must've been here for centuries. Think of all the people! This city must be huge.” He indicated with his head towards the smoking spires punching up into the grey smog. In the distance a klaxon bleated insistently a few times, before falling back into silence. The Doctor began walking towards the squat cityscape, leaving Rose to follow in his wake. He was perpetually gazing around, taking in every detail of the place with a mix of inspection and wonder. Rose was amazed he could find anything to entice his attention in such a dump. She was eager to reach the city; where there were people, there'd be hot food, and maybe someone to tell them exactly how far they'd gone off-track. The Doctor had told her there wouldn't be any humans out here; at this point in time, humanity should still be learning the fine art of banging rocks together. But then how were people speaking some mix of Earth languages out here? It didn't make any sense. She gazed up at the sky, wishing she could see the constellations overhead, but the turgid fog blocked out everything, squatting possessively over the landscape like an over-protective parent. She couldn't even make out the planet's Sun, though there must be one, because a thin grey light illuminated the landscape. It might as well haven't have tried, though; what little architecture they came across was the same boring blocky cement that had made up the sewage canals.
After a mile or so, they came to the back of a ragged crowd making their way towards the city. They were human, to Rose's surprise, though the Doctor showed no signals if he was caught unawares by this. They joined the crowd, the Doctor sauntering along and taking in everything with his casual gaze, getting more than a couple of odd looks in return. His spritely plumage of hair and well-kept, casual appearance was at distinct odds with the ragged clothes of those around him, what colours there were dimmed to a near-uniform grey by generations of use. The parts that did stand out were mostly repairs; patches of obviously new material sewn over worn knees, split seams repaired with threads that seemed garish in their newness. The figures on display matched their wardrobe; hunched spines supporting heads long used to bending in toil or genuflection, no longer bothering to look up, their feet carrying them in a weary manner that suggested they had travelled the same route daily for many years. The buildings they poured out of looked like factories to Rose's eye, the fields of sewer irrigation reluctantly giving way to a squalid industrial environment, wire fences clawing up from the ground to guard bland rectangles of grey concrete. What signs there were were in the foreign tongue the Doctor had recognised earlier, but Rose did notice one recurring theme; an image of a two-headed eagle, stencilled in black along the tops or bottoms of most of the signs. She pointed it out to the Doctor, who shrugged.
“Perhaps it's a local deity.”
Rose thought back to the poster in the sewers; that had had one of the strange eagles on it, too. She frowned, imagining a collossal two-headed beast ruling over these dejected people, kept in line by it's army of robot soldiers. It wasn't a pleasant thought.
The crowd had slowed, and Rose craned her neck to see what was causing the hold up.
“Doctor! There's a group of soldiers checking the crowd. What should we do?”
“Find out what they want, I guess.” He gave her a smile which she suspected was trying to be reassuring, but from the Doctor such expressions were always slightly off-kilter. As they got closer, she identified a balding man with a long goatee as the leader of the group. His dress was more ornate, his greatcoat decorated with gold trim and a rich burgandy lining, and he held a staff with a finely-wrought golden “I” on the head. A statue of the strange two-headed bird from before perched atop the staff. She thought it looked odd, giving the whole staff a top-heavy appearance. Then the creature turned one of it's heads, and she froze. It's right-hand side had been obscured from her until now, and it seemed that that entire side of the bird's left head had been replaced, the glimmering gold feathers ending abruptly, a metal half-helm clamped on the side of it's head. And where it's right eye should be, there was only an empty socket, adorned with lights and strange devices.
The Doctor bumped into her back, and she jumped. “Now now.. Stay calm, I'm sure we'll get through this without a fuss.” He patted her on the shoulder as the last of the crowd filtered through the blockade, leaving only them. “Gentlemen!” The Doctor announced, stepping past her to greet the soldiers. “What can I do for you today?”
“Your papers.”
“Which ones? I've got so many scattered around, I lose track..”
“Ident card. Both of you.” The man with the goatee turned his interrogative glare onto the Doctor, his eyes overshadowed by bristling black eyebrows, peppered with grey. The bird squawked loudly, repositioning itself on the staff.
“Ident!” One of the heads cawed.
“Papers!” Argued the other, butting at it's sibling with it's beak.
The Doctor rummaged in his coat, pulling out his psychic paper and displaying it to the man. “Inspector Gadget. This is my assistant, Penny. We were just inspecting the factory back on the left there. You should have seen it, awful state. Rats the size of your leg..”
The man didn't seem to be paying much attention to him, his attention rapt on the psychic paper. “Emperor preserve us..” One of the soldiers uttered, raising his rifle. The other one was doubled over, vomiting onto the dirt at his feet.
“What?” The Doctor turned the psychic paper with a quizzical expression. This turned to one of horror at what he saw. The surface of the paper seemed to have liquified, flowing insidiously over the wallet he kept it in, tendrils reaching out to stick to his hands with a cloying sensation. The surface was ever-shifting, but the main theme seemed to be faces; faces pushing through the surface of the paper, screaming in agony as new faces squeezed through their cheeks, mouths, eye-sockets, in an endless recursive loop of agonized expressions. The Doctor dropped the paper with a start, gazing down at it in shock. The three men had stepped back, the two soldiers hurriedly crossing their palms over their chests in an imitation of the eagle-sigil, as the man in charge raised an intimidating-looking sword out from the length of his staff, flicking a switch upon its hilt. A crackle of electrical discharge seemed to flow up the blade, making the hair on the back of Rose's neck start to lift and buzz. With a thrust the man drove the blade through the paper, impaling it against the dirt.
When Rose looked down, the faces had gone, the borders returned to dull uniformity. The surface around the blade looked burnt, crisp edges starting to curl away from the blade as if in pain.
The Doctor recovered first, gathering his wits to look up, straight into the barrel of a snub pistol held by the bearded man. The weapon looked chunky, as if it belonged in a workshop more than a battlefield, but no less dangerous because of it. A wax seal held a tattered strip of parchment pinned to the chamber, fluttering in the wind in a strangely dainty way compared to it's metal host.
“Men! Seize these heretics!” He barked.
“Heretics! Heretics!” croaked the bird, dislodged from it's perch, flapping around their heads in agitation.
“Now hold on a minute..” The Doctor said, raising his hands.
=I=
Hive Fleet Acridus - 1,500pts
Imperial guard - 800 points
Space Marines - 2000 points 
~4100
~1660