Dean gave up on keeping track of direction nearly an age after he gave up on keeping track of time.
He might have continued counting if he'd had any sign it would help - any proof that it wasn't a fool's errand, that time or direction meant much of anything in the Empty - but he was reasonably certain it wouldn't. If that dimension (for lack of a better word) functioned remotely like Heaven, Hell, or Purgatory, time wasn't time and space… space was a joke.
Of course, after an age (and an eternity on top of that), Dean couldn't be sure what there was left to do that he hadn't already done. That wasn't so much a question that could be answered from the outside - they'd quite fully established that the Empty was under-researched by the Men of Letters, and how to track down a missing angel from the bowels of the Empty wasn't in any index either - and he had little to no clue of how to go about answering it now that he'd found a way to ask it from the inside.
Dean had tried speaking, but that didn't especially work; perhaps he was imagining it, but the words didn't much seem to last. It felt (whether true or merely perceived) as though they were simply snatched away, swallowed by something he couldn't see and wasn't sure he wanted to. It didn't much matter what he said - be it aimless words, or lyrics, or attempts to talk to entities he still hadn't found - or how he said it; they all just vanished. (He still couldn't bring himself to say one particular name, barely even to think it, but he tried more or less everything else.)
He'd given up speaking a long distance after he'd given up on keeping track of direction, which was, itself, about an age after he'd given up keeping track of time.
The practicalities didn't matter much anyway. Even if the Empty were exactly as it seemed - if every second ticking by were a second in the real world, every stride a step - and the odds as stacked against him as they most certainly seemed… well. It'd make no difference, would it? Dean wasn't one to give up - not in general and definitely not with a way to rescue Cas on the line - and he'd pulled off enough last-ditch, no-way-in-hell-it's-gonna-work plans to know that what should work had no sway over what did work. The fact that even he couldn't deny that the idea of successfully carrying out said rescue plan felt just a touch unrealistic didn't matter either.
For one thing, he was starting to think that the Empty was contributing to that hopelessness. The feeling permeated the air - a weighted sensation, like just moving or thinking or breathing took ten times the effort it usually would - like one of those dreams where you could keep trying to do the same thing, over and over, and never get it done. For all Dean knew why he was there and what he was doing - the importance of it ingrained deeply enough that he couldn't forget it if he wanted to - the Empty itself was trying just as hard to wrest his determination away from him. It was doomed to fail, of course, but it tried damned hard.
That wasn't even counting the well-nigh soporific quality to the air. The way that dragging sensation - like moving through molasses - increased the desire to just… sleep. For there being nothing to see - less than nothing to see, really, since it was dark enough that dark seemed too light a term - Dean's eyes burned with so severe an exhaustion that he half expected to just keel over and pass out. (It'd be rather embarrassing to faint, mid-rescue, like the Victorian protagonist of some romance novel, and he'd much rather that not be his way of shuffling off the mortal coil for the final time.) The Empty apparently overestimated the power of exhaustion when confronted with a lifetime of three-hour nights and the quantity of willpower necessary to have torn a hole between the dimensions.
After an age, and an eternity, and aeon on top of that, Dean finally stopped walking.
It wasn't permanent - merely a break to get his bearings and figure out what bases he hadn't yet covered - but it was a pause. The tacky ooze at his feet fell silent, content with lying in stagnation once it finished sucking greedily at the soles of his boots, and the noise, for a second, vanished completely. There was only nothingness: a total absence of light and sound and stillness.
It was overwhelming, and too much, and yet there was still no Cas and that simply couldn't stand so there also wasn't nearly enough.
A shudder passed through the Empty then. It wasn't a physical sensation like an earthquake so much as it was a sensation that something had changed. A ripple, passing through the entire realm, of what could only be termed intensification, All at once, the silence, the hopelessness, the exhaustion simply amplified, building in a crescendo that couldn't be named but could somehow be felt.
And then, just as suddenly as it had started, it stopped.
The ripple ceased its propagation, and the world - such as the world could be perceived - stilled. The hopelessness didn't completely abate, just like the silence didn't lift and the exhaustion didn't dissipate, but it lost some of the intensity and landed firmly in the region of tolerable enough.
When Dean adjusted to the fact that the sensation was gone, he somehow found himself on his knees. The slime coating the floor - to the extent there was a floor to coat - was cold and sticky as it seeped through the cloth at his knees, grasping at the material like the ooze itself was alive and eager to devour anything it touched. (It was disgusting, and probably unsafe, and far too evocative of that library and its blood-soaked wooden floors. For a second, Dean couldn't stop himself from clawing at it, fingers digging in and pulling at the strands to just get them off. It didn't work.)
Dean had long made his peace with emptiness being a close companion, but he'd never thought it quite so literal. It had sat in the Impala and slept in motel rooms and (according to Famine) lived inside him, yes, but it had never oozed into his clothing or dripped from his fingers or caked under his nails to quite the same degree. It had never seemed quite so sentient - quite so overwhelming - as it did right then, surrounded by an abstraction rendered concrete.
He forced himself upright nonetheless, numb fingers still clenched tightly in his jeans until that particular section of cloth slid too far away and yanked itself free. Circulation restored itself with the painful prickling of pins and needles, and even flexing his fingers did little to fix it; he could barely feel the thickened cloth that represented the hem of his pockets.
He could, however, feel the lump of thick plastic sitting inside said pocket, more because his wrist hit it by chance than because of any tactile sensitivity from the fingers themselves. He still couldn't make out any sensation, but he had enough dexterity left to fumble the thing free and try to see what it was. He could, but only barely, and he didn't really need to anyway; the feel of it was familiar enough to place without difficulty.
Dean had never been more grateful to see a tape player in his life.
He wasn't fully sure it would even work, to be fair - if he couldn't hear himself, then how could he expect to hear something not himself? - but that wasn't really important; just the idea was enough. He'd run out of thoughts at some point, and more or less forgotten sound just after (or, at least, forgotten any sound that wasn't the echo of his own footfalls), but a tape - and, wonder of all wonders, a track list - would be more than enough to keep the overpowering silence buried for a little longer. They wouldn't be his own words, but that didn't matter much at all; they were words and music and noise and the idea was tempting enough to have him fumbling at the eject button.
When he finally got the tape out, he almost dropped it.
By rights, it shouldn't have been much of a surprise. He'd just been listening to it, mere moments before he ran to the library and insisted they let him take on his rather risky plan, and that couldn't have actually been as long ago as it seemed. It wasn't something that should have been easy to forget, and nor should it have been something he brought with him, but he hadn't exactly been in the best frame of mind for a good week, so he supposed it was just to be expected.
Given his quite-probably-fatal mission was quite specifically intended to rescue Cas, he couldn't very well blame his subconscious for choosing the mixtape.
His hands still shook as he held it, harshly enough to almost dislodge it from his grasp entirely, but he managed to hold on anyway; it was far too precious to allow to fall, to permit the hungry black ooze to touch it - or, worse, consume it completely. His hands shouldn't even have been shaking, given that steadiness was a crucial skill he'd learned young to avoid dying young, but they were, and he didn't bother to question why when the answer was, quite simply, obvious. He didn't have to ask when memories chose just then to course through his head - the hours he'd spent making the mixtape in the first place, the god-awful anxiety of preparing to hand it over, the hurt-worried-anger of when Cas tried to give it back - even though he'd never invited them in.
With them came other memories. Better memories. Worse memories. In-between memories and half-and-half memories. Shrieks in a gas station and shattered glass and sparks cascading down from a barn's half-rotted rafters. Blood and fire and turned-around looks for one last glimpse he shouldn't have needed because betrayal should have (but didn't) take away the care. So much death and loss and despair, but, with it, the relief of safety, the joy of resurrection, the perpetual (if temporary) returns. Personal space shared and stares from too close and that easy knowing that felt, simultaneously, so, so natural and far too alien.
By the time Dean looked up, he was crying. And Cas… Cas was just there.
He looked like he had back in that library, collapsed on the floor in some grotesque mockery of sleep, peaceful and yet not. There was no blood surrounding him as there had been, but it had been replaced, supplanted by the sickly shining blackness that covered everything in the Empty; Dean wasn't sure whether that was better or worse. He could still see the gaping edges of the wound the angel blade had left behind, and it didn't change the fact that he was dead, whether he looked like it or not.
None of that - the death or the sludge or even the horrible, weighty guilt - did anything to stop Dean from bolting over. From tangling his hand in the stained, dirty trench coat as he had so many times before - after the Leviathans, the cloth scummy and mold-covered; in Purgatory, with Cas so gloriously alive underneath; before and during and after any of the other near-death experiences they had where he could actually get away with it - and heaving the dead (don't think it, don't think it, don't-) weight into his lap and just sitting. The name he hadn't been able to say for so long spilled out again and again, everything forgotten under the fact that he'd damn well found him and maybe - just maybe - there was a chance he could wake him up.
It didn't work, but he couldn't just stop so he just kept going and going and going. It was a litany.
A prayer.
A devotion.
A supplication.
For Cas.
"So," he heard behind him eventually. "Helpful and dreamy finally paid the final price of knowing a Winchester, huh?" It was a familiar voice, and he didn't have to turn around to place it. For a moment, he let himself stay perfectly still. "Pointless, bloody sacrifice for no reason." A hum. "Shoulda known it'd happen eventually. Happened to me, after all."