A/N: This fanfic has a fun twist to it – it is going to be partially played like a pen-and-paper roleplaying game, somewhat like Dungeons and Dragons. However, the roleplaying game I'm going to use as a basis is Black Crusade from the Warhammer 40,000 franchise. Don't worry – while this is technically a crossover, no prior knowledge of WH40K will be needed to understand this story. The powers Chell has in this story are the same ones that a psyker could have in WH40K. Black Crusade was chosen out of all the WH40K roleplaying games because it had the widest variety of psychic powers out of all the ones that I've played – as well as some lore reasons.

I've made a character sheet for Chell using the usual character creation process from Black Crusade, picking abilities that made sense for her and omitting abilities that a character would normally start with, but wouldn't make sense for her to have, like lore and language skills. Whenever she wants to use a psychic power, I'll roll dice to see if she succeeds, and what unintended consequences may occur. I'll only treat it like a roleplaying game for WH40K related stuff; I'm not going to roll to see if she can solve a test or do anything she can do in Portal 2. This means that I don't really know what's going to happen in this fic – or if Chell even survives to see the end.

It is the 41st millennium…

For more than a hundred centuries the Emperor has sat immobile on the Golden Throne of Earth. He is the master of mankind by the will of the gods, and master of a million worlds by the might of his inexhaustible armies. He is a rotting carcass writhing invisibly with power from the Dark Age of Technology. He is the carrion lord of the Imperium for whom a thousand souls are sacrificed every day, so that he may never truly die.

Yet in his deathless state, the Emperor continues his eternal vigilance. Mighty battlefleets cross the Daemon-infested miasma of the Warp, the only route between distant stars, their way lit by the Astronomicon, the psychic manifestation of the Emperor's will. Greatest amongst his soldiers are the Adeptus Astartes, the Space Marines, bio-engineered super-warriors. Their comrades in arms are legion: the Imperial Guard and the countless planetary defense forces, the ever-vigilant Inquisition and the Tech-Priests of the Adeptus Mechanicus, to name but a few. But for all their multitudes, they are barely enough to hold off the ever-present threat from aliens, heretics, mutants – and worse.

To be a man in such times is to be one amongst untold billions. It is to live in the cruelest and most bloody regime imaginable. Forget the power of technology and science, for so much has been forgotten, never to be re-learned. Forget the promise of progress and understanding, for in the grim dark future there is only war. There is no peace amongst the stars, only an eternity of carnage and slaughter, and the laughter of thirsting gods.

Yet Chell is unaware of any of this. For tens of thousands of years, the Aperture Science facility sat untainted by the wars of the outside, holding scientific knowledge long forgotten that would now be called heresy. But despite her isolation, Chell's existence has not gone entirely unnoticed, and the darkness of the Warp has crept is way inside her mind and inside Aperture…

"Probably ought to bring you up to speed on something right now," the core said as the door slid open and Chell walked into the decaying hallway beyond it, "In order to escape, we're going to have to through HER chamber. And she will probably kill us if, if, she's, um, awake. If you want to just call it quits, we could just sit here. Forever. That's an option. Option A: Sit here. Do nothing. Option B: Go through there, and if she's alive, she'll almost certainly kill us."

Through the hallway's windows, Chell could see another hallway, suspended crookedly across a chasm, leading to a large, familiar chamber. She cautiously crept around the corner and into said hallway, which was tilting to one side. The core grew visibly more nervous as she came closer to the door on the other end.

"Okay, I'm going to lay my cards on the table: I don't wanna do it. I don't wanna go in there! "Don't... Don't go in there!" He begged, nearly panicking as door opened and she entered the chamber, "Don't – She's off. She's off! Don't panic over it, she's off. All fine, on we go!"

She approached the destroyed remains of the AI, half expecting her to spring back to life and attack. Out of the corner of her eye, she noticed a small pool of water. Oddly, the reflections of herself and the ceiling in the pool seemed distorted even though the pool looked still.

"There she is... What a nasty piece of work she was, honestly," the core said, shaking his entire body as though he were shaking his head, "Like a proper maniac. You know who ended up, do you know who ended up taking her down in the end? You're not gonna believe this. A human. You, ah, you alright there, mate? You're starin' into space a bit..."

Chell tore her eyes from the pool and shook herself out of it, concluding there must be some chemical in the water, even though something had seemed off about every reflection she had seen since waking up in this facility. The whispering in the back of her mind had grown a little louder as well, but she forced herself to ignore it and focus. She could not afford to worry about whatever brain damage she had gotten from being in suspension until she got out of this facility. She made her way to the other end of the chamber.

"Anyway, apparently this human escaped and no one's seen him since," the core went on. He continued talking as she found her way out of the chamber and down onto a catwalk. They ended up in a small, circular room with a dock in the middle for the core and levers covering the walls.

"This is the main breaker room. Look for a switch that says ESCAPE POD," the core instructed, "Don't touch anything else. Not interested in anything else. Don't touch anything else. Don't even look at anything else, just – well, obviously you've got to look at everything else to find ESCAPE POD, but as soon as you've looked at something and it doesn't say ESCAPE POD, look at something else, look at the next thing. Alright? Don't touch anything else or look at any – well, look at other things but don't... you understand." Chell had tuned him out long before he got to the end of his rant. "Can you see it anywhere? I can't see it anywhere," he said after only a few seconds of looking, "Uh, tell you what, plug me in and I'll turn the lights on."

She plugged him into the dock in the middle of the room and soon after the lights came on.

"Let there be light! That was, uh... God. I was quoting God," the core said. Suddenly, the floor rotated. "Oh! Look at that, it's turning. Ominous. But probably fine. Long as it doesn't start moving up..." Almost immediately, two klaxons rang out, and the floor began moving up, flipping every switch in the breaker room as it did so.

"It's... It's moving up. Okay, okay! No, don't worry! I've got it I've got it I've got it! This should slow it down!" the core reassured her confidently. The floor paused briefly before moving up even faster. "No. Makes it go faster," he said, disappointed.

"Powerup initiated," came the male voice that earlier had guided Chell through test chambers as the floor came to halt, leaving them before the remains of the dead AI.

"Don't panic! Alright? Stop panicking!" the core said in a panicked voice. The massive AI began to move, wires pulling its head to its body as its optic flashed a dull yellow. "I can still stop this," the core insisted, "Ahh. Oh, there's a password. It's fine. I'll just hack it. No problem... um..."

Chell tuned him out once more and watched her old enemy reassemble herself. Cables dragged the entire massive machine into the air. Sparks flew from her as she swung and rotated.

"Powerup complete," said the announcer. Chell was normally able to keep calm in these sorts of situations, but she felt her heart begin to race and her breathing quicken. The whispering was louder than ever. It became hard to think. She felt energy well up inside her as her head began to hurt.

The AI suddenly stilled, focusing her optic on Chell.

"Oh... it's you," GLaDOS said, her voice deceptively calm, "It's been a long time. How have you been?"

The feeling surging in Chell's head was becoming too much. She was certain she was going to have a panic attack or something. Suddenly, though, it was all released.

"I've been really busy being dead. You know, after you-ack!" GLaDOS flinched as her optic shattered.

Chell stepped back, eyes widening in confusion as sparks flew from the AI. "What did you do?" she hissed, shaking her core.

The air suddenly felt like it was vibrating. The world around her began to look transparent, and through the transparency, Chell saw a bizarre world made up of twisting landscapes of impossible geometry that were constantly reshaping themselves with swirling storms of energy in the background. It was like looking at a visual paradox, except horrific and constantly changing to become more and more mind-boggling. Just looking at it made her head swim and her reality come into question.

In that world, seemingly pressed up against and clawing at a thin veil separating them from her world, were horrific creatures.

Claws, tentacles, pulsating skins, toothy grins, bloodstained swords, butcher knives, whips and chains...

Their laughter echoed in both Chell's ears and mind. She fell back against the wall behind her, holding up her portal gun as if it was a weapon, trembling. They all seemed to be glaring, laughing, directly at her, looking through her into her soul.

There was a strange sputtering sound, so she tore her eyes from the terrifying creatures and saw that GLaDOS had once again gone limp. The core, meanwhile, was staring straight ahead, his blue optic a tiny point.

Suddenly, the creatures and their strange world disappeared, and everything was back to normal. Shivering, Chell got up. GLaDOS was still limp, and the core was still staring silently. While she tried to compose herself and make sense of what just happened, GLaDOS started to move again. She immediately focused her gaze on Chell.

"Oh... it's you," GLaDOS said, just as she did before, her optic still sparking, "It's been a long time. How have you been? I've been really busy being dead. You know, after you murdered me."

Two mechanical claws descended from the ceiling, snatching up both Chell and the core. The core seemed to snap out of it, his optic widening again and looking around. "W-what-" he began before GLaDOS squeezed him into silence.

"Okay. Look. We both said a lot of things that you're going to regret," she paused as the claw crushed the core, sending sparks flying and making his optic go dark, "But I think we can put our differences behind us," GLaDOS went on as she tossed the core away, "For science. You monster." The claw began to carry her towards the incinerator. "I will say, though, that since you went to all the trouble of waking me up, you must really, really love to test." The incinerator slid open. "I love it too. There's just one small thing we need to take care of first."

With that, Chell was dropped into the incinerator. Normally, the crushers snapping shut just in front of her as she fell through the shaft would have frightened her, but after what she had just been through, they barely registered. When she landed, her head was still spinning as it tried and failed to comprehend the twisted world she had seen. She was also troubled by GLaDOS' apparent memory loss – hadn't she been there? Didn't she see it? Unless it never happened...

That had to be it, Chell decided as she made her way across fallen scaffolding that formed a bridge across the flaming pit of the incinerator. It was just a hallucination. That core did say she probably had brain damage, after all. She had to ignore it and focus on the real world.

I'm afraid it's very real, came a deep voice, chuckling. Chell froze in place and looked around, but she was completely alone. You were granted a great gift. I can help you use it. The fact that it hasn't killed you already is promising, the voice came again.

It's just a voice in my head, Chell told herself firmly, It's just brain damage...

"There it is," GLaDOS said as Chell came upon the dual portal device, "Hold on..." The panels covering it lifted themselves up. "There." Chell took the device and the AI continued, "Good. You have a dual portal device. There should be a way back to the testing area up ahead."

I'll prove I am indeed real, came the voice, The first test chamber will involve... deadly lasers. The voice laughed and then went silent.

"Once testing starts, I'm required by protocol to keep interaction with you to a minimum. Luckily, we haven't started testing yet. This will be our only chance to talk," GLaDOS explained as Chell began making her way through a destroyed test chamber. "Here, let me get that for you," she said as a panel flipped down so she could portal up to a ledge. "Do you know the biggest lesson I learned from what you did? I discovered I have a sort of black-box quick-save feature. In the event of a catastrophic failure, the last two minutes of my life are preserved for analysis. I was able – well, forced really – to relive you killing me. Again and again. Forever," she continued, "You know, if you'd done that to somebody else, they might devote their existence to exacting revenge... Luckily I'm a bigger person than that. I'm happy to put this all behind us and get back to work. After all, we've got a lot to do, and only sixty more years to do it. More or less. I don't have the actuarial tables in front of me"

Chell had gotten to what looked like the beginning of the test chamber. A panel with the number 19 lit up as she approached it and turned down a hallway blocked by panels lying limply on the ground. "I'll just move that out of the way for you. This place really is a wreck," GLaDOS said as the panels weakly moved aside, "But the important thing is you're back. With me. And now I'm on to all your little tricks. So there's nothing to stop us from testing... for the rest of your life." The door at the end of the hallway opened to a stairway leading down to an elevator. Chell quickly entered it, figuring as it descended that at least testing would help her ignore any voices she might hear. "After that... who knows? I might take up a hobby. Reanimating the dead, maybe."

The elevator came to a halt in the first test chamber.

"Sorry about the mess," GLaDOS said as Chell exited the elevator, "I've really let this place go since you killed me. By the way, thanks for that."

"Sarcasm Self-Test complete," came the announcer's cheerful voice.

"Oh good, that's back online," GLaDOS continued, "I'll start getting everything else working while you perform this first simple test. Which involves deadly lasers and how test subjects react when locked in a room with deadly lasers."

Involves deadly lasers. Those words made Chell's blood run cold and she froze in the test chamber's entrance. She thought she heard laughter in the back of her mind. Sure enough, after some time the laser activated. She regained her composure and quickly solved the test.

"Not bad. I forgot how good you are at this," GLaDOS flatly praised her as she exited the test, "You should pace yourself, though. We have a lot of tests to do."

An elevator descended into the center of the elevator room and opened.

Wait, came the voice again before she could get on it, Humor me. Try lifting a piece of rubble with your mind. It's a simple technique known as Mind over Matter; imagine reaching out with hands of spectral presence.

Spectral presence, sure, Chell skeptically as she looked at the rubble cluttering the room. She was wary of what GLaDOS might do if she took too long to get on the elevator, but maybe shutting this voice up would be worth it. She looked at a small piece of rubble on the ground and imagined an invisible hand reaching out of her and grabbing it. She felt energy well up in her like before, and the piece of rubble slowly rose from the pile. She pictured the hand bringing it to her and it came, drifting slowly through the air. She held out her hand as it hovered in front of her and released it, expecting it to fall but instead it drifted slowly down into her palm. She stared at it, dumbfounded, wondering if she was somehow hallucinating again even though her head felt clear, unlike before when she saw the terrifying other world and the creatures within it.

"Have you forgotten how to use the elevator? All you have to do is step inside," GLaDOS snapped.

Chell dropped the piece of rubble and boarded the elevator, which immediately descended to the next test chamber.

A/N: Writing this first chapter taught me a valuable lesson. Don't decide to use random chance in a story and then proceed to make plans. I planned to slowly introduce Chell to her powers and the world that they came from, like how most fantasy stories about a character discovering magic handle it. But then I rolled the dice. And the dice laughed. If you're curious, what follows is a lengthy explanation of the WH40K rules applied in this chapter, what the dice rolls were, and why things happened the way they did. I tried to keep it short, but a lot of stuff happened in this chapter that needed explanation. No, if you're not interested, you do not need to read it to understand the story.

If you're unfamiliar with pencil-and-paper RPGs in which you roll dice to determine what happens, we often use the term XdY, where X is the number of dice rolled and Y is the number of sides each die has. If a rulebook says that a certain attack does 2d6 damage, then you roll 2 six-sided dice and add the results to figure out how much damage you did with that attack. In WH40K, we primarily use d100. One hundred-sided dice do not exist as far as I know, so we roll two d10s with one d10 giving the tens place and the other giving the ones place to get a number between 1 and 100. These are also called percentile dice.

The most basic action you do in a WH40K roleplaying game is a characteristic test. Each character has 9 characteristics with scores between 1 and 100: Weapons Skill (WS), Ballistic Skill (BS), Strength (S), Toughness (T), Agility (AG), Intelligence (INT), Perception (PER), Willpower (WP), and Fellowship (FEL). To see if your character succeeds in doing an action related to a characteristic, you roll a d100 and if the result is equal to or less than your character's characteristic score, your character succeeds. For every 10 points less than the characteristic score that you roll, you get a degree of success. Likewise, for every 10 points above the score that you roll, you get a degree of failure. For example, if you have a characteristic score of 53 and roll a 31, you succeed by 2 degrees. Psykers like Chell have another stat called Psy Rating (PR), which indicates their psychic power. Psykers in this game start with a PR of 3, and so Chell's PR is 3.

The first instance of psychic powers being used was after GLaDOS wakes up. Chell's psychic powers manifest for the first time in the form of her accidentally using a psychic technique called Force Bolt, in which you shoot an invisible projectile, on GLaDOS. When using a psychic power, the first step is to pick one of three power levels: Fettered, where you hold back and cannot cause psychic phenomena; Unfettered, which is standard but there is a chance to cause psychic phenomena; and Push, where you go beyond your normal limits and are guaranteed to cause psychic phenomena. Since this is Chell's first time using a psychic power, I went with Unfettered – she doesn't yet know how to hold herself back or push her limits. Force Bolt, like most psychic powers, require a willpower test to use, and Chell has a Willpower score of 61. However, Force Bolt is a fairly simple technique, and thus is given an Ordinary (+10) challenge rating, so we add 10 to her Willpower. We also add 5 for each point of PR, so altogether we have 61 + 10 + 15 = 86. To successfully use Force Bolt, Chell must roll an 86 or lower.

I roll for her and get a 33. Success! But there's a problem. When using the Unfettered power level, psychic phenomena occurs if you roll a number whose first digit is the same as its second, like 33. Leave it to a dangerous mute lunatic to cause psychic phenomena the first time she uses a psychic power. There are a number of different psychic phenomena that can occur. To figure out which one, roll a d100 and consult the Psychic Phenomena table in the rulebook. In general, higher numbers give you worse results.

I roll and get a 94. Remember when I said that higher numbers give you worse phenomena? Well, if you roll a 75 or higher, you instead get Perils of the Warp. Perils of the Warp are a special type of psychic phenomena that are much worse than normal psychic phenomena. Leave it to a dangerous mute lunatic to cause Perils of the Warp the first time she uses a psychic power. Considering what a lot of Perils of the Warp entail, I wouldn't have been surprised at this point if Chell died and took GLaDOS and Wheatley down with her. Like with psychic phenomena, to determine what Perils of the Warp you get, roll a d100 and consult the Perils of the Warp table. I roll and get a 69, which corresponds to:

Rending the Veil: The air vibrates with images of cackling daemons and the kaleidoscopic taint of the warp is rendered visible. All sentient creatures (any creature with an Intelligence characteristic) within 1d100 meters (rolled and got 99 meters) must test against Fear (2). The psyker must Test against Fear (4) instead. This effect lasts for 1d5 rounds.

So now Chell, GLaDOS, and Wheatley must all take a Fear test. A Fear test is a Willpower test with the level of Fear corresponding to what modifier you apply to your Willpower. Chell must take a Fear (4) test, which means she has to apply a -30 modifier to her Willpower score. So, in order to pass the Fear test, she must roll a 31 or under. I roll for her and get a 71, which is 4 degrees of failure. When you fail a Fear test, you must roll a d100 and consult the Shock table in the rulebook, adding 10 points for every degree of failure, to determine how your character is affected by fear. Like with psychic phenomena, higher numbers are worse. Chell failed by 4 degrees, so I will add 40 to whatever she rolls for the Shock table. She rolls an 11 (finally some good luck for Chell), which means she gets a 51 on the Shock table, which corresponds to:

Reeling with shock, the character slowly backs away from the thing that confronts him. The character cannot willingly approach the object of his Fear, but may otherwise act normally, albeit with a –10 penalty on all tests for the rest of the Encounter.

Wheatley is up next. I decided to give him a Willpower of 35. A Fear (2) test means he gets a -10 modifier and must roll under a 25 to succeed. He rolls a 57, so he fails by 3 degrees. On the Shock table, he rolls a 48, meaning he gets a 78, which is:

The character is frozen in terror. He may take no Actions until he snaps out of it. After snapping out of it, the character makes all tests with a –10 penalty for the rest of the Encounter.

Now on to GLaDOS. She and Chell are pretty evenly matched in terms of willpower, so I give her a Willpower score of 60. Like Wheatley, she needs to take a Fear (2) test, meaning she gets a -10 modifier. She has the highest odds of succeeding out of everyone, but gets the worst luck. She rolls a 94, 4 degrees of failure. She then rolls a 68, giving her a 108 on the Shock table. This corresponds to:

The character faints dead away, and remains unconscious for 1d5 rounds. Once he regains consciousness, he is still shaken and suffer a –10 penalty to all tests for the remainder of the Encounter.

Maybe this is a good thing. Descriptions of the Warp are vague, but from what I gather, if hearing a paradox can kill an AI, GLaDOS would almost certainly not survive looking into the Warp. So... Let's just say that as soon as she saw it, her mainframe shut her down and deleted the memory. And maybe having a shattered optic helped protect her as well? That makes sense, right?

Now, some of the rules I've listed state something should last a certain number of rounds. But, we're not in combat, so rounds aren't really used. I just went with what timing made narrative sense. Also, although Force Bolt is an attack, I didn't bother with rolling damage since that would require deciding how many hit points and armor points to give GLaDOS, and since she's guaranteed to not die since it's a weak attack and repair herself before we see her again, there really wasn't much point.

After the Rending the Veil effect ends, GLaDOS wakes up and I decide to give Wheatley a chance to "snap out of it." In order to snap out of it, a character must pass a Willpower test. His Willpower is 35, and he rolls an 8, so he succeeds. Later on, I have Chell use a second psychic power, this time Mind over Matter. Using Mind over Matter requires a Willpower test and has a challenge rating of Routine (+20). So, add 20 to her Willpower of 61 and the 15 she gets from her Psy Rating and we get 96. However, rolling a 91 or higher always results in an automatic failure when using psychic powers regards of other factors, so if she rolled, say, a 93, she still would have failed. Luckily, she rolls a 64 and succeeds.