A/N: Aaand this is it. Feels like yesterday that I began writing this, and we've reached the end already. Wow. I can only hope it won't disappoint!
Thanks a lot to everyone who's read/reviewed/faved/liked/kudo-ed this. I hope you had a good time reading - I sure had a good time writing.

"Summer in Gravity Falls can last as long as you want it to! I just need you to get a little gizmo for me from your uncle."

When Gravity Falls and Earth becomes sky...

"Just a little more summer."

… Fear the Beast with just one eye.

"At last! At long, long last! The gateway between worlds has opened! The event one billion years prophesized has finally come to pass! The day has come! The world is finally mine!"

The moment the glass breaks and the rift opens is a moment of pure, unbridled triumph. Everything Bill has felt, everything he has achieved in billions of years was nothing, nothing compared to this. The last dimension to elude him, the one he's always wanted, is finally his - a world full of possibilities, even more so that he's there to liberate it from everything putting a stop to all that wonderful, wonderful potential.

His victory is complete. The longest game of chess has come to an end, and he's won.

"This party never stops! Time is dead and meaning has no meaning! Existence is upside-down and I reign supreme! WELCOME, ONE AND ALL, TO WEIRDMAGEDDON!"

He's not at all surprised when good old Fordsy tries to shoot him back into the gateway. He's been working to stop him and developing weapons half of his pathetically short life, after all; to be honest, Bill would have been disappointed if he hadn't tried.

And after he fails, because of course he fails, Bill feels generous enough to extend his offer once again. Maybe it's the sense of triumph making him sentimental.

"Now don't look so sour, Fordsy. It's not too late to join me. With that extra finger, you'd fit right in with my freaks!"

I'd have preferred to die without seeing any of this!

"I'll die before I join you! I know your weakness, Bill!"

… Ah well. No one can say Bill didn't try. The stubborn goat can have it his way, and Bill could really use a back scratcher made of solid gold.

He doesn't worry when Pine Tree gets away. He doesn't worry when Time Baby shows up, and relishes in getting him out of the way. He doesn't worry when Gideon turns on him. He doesn't worry when Pine Tree reaches Shooting Star's Bubble, and he doesn't worry when they burst it - because at that point he's busy dealing with Ford, to get that dumb barrier down and let him out of that stupid town.

Sixer is really pushing his luck - he should know by now that there is nothing Bill loathes as much as being shut in, nothing he's not willing to do in order to get out - but Bill is willing to repeat his offer one more time.

"Listen, Ford, if you just tell me that equation, finally your dimension will be free. Anything will be possible. I'll remake a fun world- a better world! A party that never ends with a host that never dies! No more restrictions! No more laws! You'd be one of us. All-powerful. Greater than anything you've imagined! And all I need is your help."

All-knowing! All-seeing! All-powerful! You can be, too! I thought you were the smart guy. Just join up.

You're insane.

"You're insane if you think I'll help you!"

Very well. If this is how he wants it to be, so be it. One way or another, he will make him talk. As Ford just said, he is insane. And he has long since forgotten what mercy even feels like.

He doesn't worry when the mortals start fighting back. He should have.

The door slams shut. The fire flares up. Bill understands. And he remembers, all of a sudden, what panic feels like.

"Let me outta here! Let me OUT! Why isn't this working?"

Panic turns into something else, something he fails to recognize as despair. It is hard to name emotions he has not felt in billions of years - but that makes them all the more frightening. Fright, too, is something he had forgotten all about. For the first time since he can remember, Bill doesn't know what to do. For the first since he began existing, he falls on his knees.

No, no, no, no, NO!

"Hey, look at me. Turn around and look at me, you one-eyed demon!"

Stanley Pines towers above him. Stanley Pines, the one and only mortal to have tricked him - the very last person he will ever see. And for a moment the All-Seeing Eye doesn't want to look, because if he cannot see something it means it cannot be real. This cannot be happening.

But it is happening, and he does turn. He looks up, to a hard-set mouth and eyes that reflect the flames all around them; for a moment, they seem to be burning with a fire of their own. "You're a real wise-guy, but you made one fatal mistake: you messed with my family!"

So tell me - what was my brother's name?

Flames close in a circle around him, terror sets in, and Bill stands for one last, desperate attempt at bargaining.

"You're making a mistake! I'll give you anything! Money! Fame! Riches! Infinite power! Your own galaxy! Please!"

Have mercy! Please! We'll do anything!

WHAT WAS MY BROTHER'S NAME?

You messed with my family!

"No!"

Stanley Pines says nothing: he just stares, and as his form begins distorting - as he feels everything he is and has ever been being torn apart despite his struggle to hold on, to keep himself together - Bill Cipher knows that he won't yield, that no amount of bargaining or begging will save him.

"What's happening to me?"

He knows what's happening, he knows it well - and as he loses control over his own being, he knows there is only one chance for him not to disappear here and now. He refuses to go, refuses to make this his last day, he refuses to let them and their rules win.

A-X-O-L-O-T-L! My time has come to burn! I invoke the ancient power that I may return!

He doesn't know why he screams Stanley Pines' name. He doesn't know why he rushes towards him, knowing full well that he's barely holding it together, that there is nothing he can do - and a well-placed punch is all that it takes to make him shatter.

He screams.

It is the last thing he remembers doing before darkness falls.

His screams echo through the fog, but no one answers. No one is there to hear: there is only him, wandering in the twisted paths of his own mind, unable to leave it, unable to tell how much time has passed - hours, days, millennia or more than that - while a thick fog makes it difficult for him to see anything at all. The All-Seeing Eye, unable to see where he's even going.

Would be funny enough to laugh at, if he wasn't just a bit too busy screaming endlessly.

He still exists, for they were unable to destroy energy, but he is more of a prisoner than he's ever been. It should anger him, fuel him, get him planning for bloody revenge to unleash on the multiverse the day he's finally out of that prison of stone. It should, but it does not. Instead, it frightens him - and that is one thing Bill has no idea how to deal with.

"Let me out of here! SOMEONE! LET ME OUT OF HERE!" he shrieks. Again, he gets no response but the echo of his own voice. Bill lets himself drop on the ground - on what ground is to be found within one's mind - and presses both hands on his eye, trying to keep himself from screaming again. What leaves him is a keening sound.

Where are the others? Where have they gone? He's unable to see anything that's happening outside his prison, and it's something so alien to him that he may as well have become blind. Have they been sucked back in the Nightmare Realm? If so, there is no hope they may find him - not with the gateway between dimension, the one he worked so hard to open, closed once again. They don't have the brains or the means to open it again.

This was not supposed to happen, it's nothing like the future he foresaw. Why wouldn't the mortals just give up? They were supposed to give up. They were supposed to surrender and cower. They were supposed to let him do his thing and liberate their dimension. This was not supposed to-

This should not have happened!

Shut up.

YOU SHOULD NOT HAVE HAPPENED!

"No no no no shut up shut up SHUT UP!" Bill screeches, panic rearing up its head again. Whoever this voice belongs to, he doesn't want to hear it. He doesn't want to listen, and he tries to run, knowing fully that he can't possible outrun something that is echoing in his own mind.

The attempt is short-lived as it's useless, because only moments later he slams against something that was hidden in the fog and falls back, mind still reeling. He looks up to see, through the milky white fog, the outline of a door - a door kept locked by heavy chains and a formidable padlock.

… A locked door? Why is there a locked door in his mind? He has no memory of ever locking any memories away - but then again, that would be the point, wouldn't it?

Confusion overriding the lingering panic, Bill stands and reaches up to touch the padlock. He pauses for a moment, then he ignites his hand. It catches fire, and so do the chains; they flare brightly against his eye only for a moment before turning into ash and falling off, leaving the old wooden door unmarred.

For a moment - only a moment - he hesitates. There must be a reason if he decided to lock those memories away. Maybe he's better off leaving it alone. Maybe… maybe…

Bill scowls, and his hand closes on the handle. It's not like things can get any worse, can they? A peek won't change anything. There shouldn't be a locked door in his mind: he's had enough of being shut out of places, even if it was by his own will. If he doesn't like what he sees, he'll just close the door again. But at least he will know.

They took everything else. I'll take back what I can.

Bill Cipher tightens his grip on the door's handle, and pushes it down.

The door opens slowly, with the kind of creaking sound doors only make when everything is silent and you're trying not to be heard. Thankfully, his parents are sleeping at the end of the hallway and don't hear a thing - but Liam does, and the moment Bill peers inside a flashlight is pointed straight in his eye.

"Hey!"

"Billy! What are you doing here?"

The light moves away and Bill opens his eye again, blinking a couple of times. Liam is sitting on the bed, the covers thrown up to his upper angle, a book on his crossed legs and the flashlight in his hand. Exactly as Bill expected to find him.

"I want a story," he whispers, closing the door of Liam's room behind him as silently as he can, and steps closer.

Liam frowns. "You should be in your room," he says, trying without much success to sound stern. He's always glad when Bill comes over, and he's terrible at hiding it.

"My room is boring."

"You should be sleeping."

"You too!"

"I'm older. I can stay up longer, and… well, mom and dad will get mad if they find out you came here!"

"Aww, you're scared."

"Am not! I just-"

Bill turns his eye into a mouth just enough to blow a raspberry, then climbs on the bed and under the covers as well. "C'mon! Read me a story!" he says, propping himself up on his elbows and looking down at the book, only to frown when he realizes he's looking at a mathematics book. "Aw, seriously! Who wants to read this stuff?"

"Some people like knowing things," Liam remarks, but he closes the book and straightens himself. That causes the covers to raise up over Bill like a small tent. "Will you be quiet if I tell you a story?"

"A scary one!"

"The scariest I can think of. It's about a pesky little Triangle who wouldn't leave his big brother in peace..."

Liam tries, he really does, and some of his stories are actually really cool, but he can't manage to actually sound scary to save his life. Still, Bill makes sure to keep his eye wide while listening to look at least a bit unnerved, and he actually jumps a couple of times to make it look like he was startled. Liam always looks so proud of himself whenever that happens, and plus playing scared gives Bill an excuse to stay in his room for the night.

"I don't wanna be all alone now!"

"You'll be fine, Bill."

"Come on! Let me stay!"

"No."

"Why not?"

"Because then I'd have to wake up early and get you in your room before mom and dad find out you're not there, that's why."

"I'll have a bad dream if I have to sleep alone! I'll wake up screaming and wake them up, and then they'll be cranky and will know you told me a scary story and-"

"Hey! That's blackmail!"

Liam tries to argue a bit, he always does, but never really means it - and, in the end, he lets Bill stay. Granted, trying to snuggle up when you happen to have angles can be a little tricky.

"Don't get your angle in my eye again," Liam grumbles, and Bill blows a raspberry against his side just for the heck of it. "Eww! Stop doing that!"

Bill laughs a bit, but quietly, so that no one will hear, and finally yawns. It's starting to get late, after all. "Night," he mumbles, and doesn't notice the brief pause before Liam answers, pulling the covers up over them both.

"... Goodnight, Billy."

They fall asleep within minutes, unaware of the universe's gears turning around them. In a matter of days, the date of Liam's Inspection will be chosen. In a matter of weeks, he will be no more and Bill will replace his not-so-scary stories with the forbidden tales of a Third Dimension he will leave behind. Their world - and the multiverse as a whole - will feel the ripples of that one day for a trillion years to come.

But right there and then, none of it has happened. Within the walls of that tiny room, in a house like countless others in the Second Dimension, time may as well have stopped. They just sleep, resting close, in one crystallized eternal moment the future is not allowed to break.

Not as long as he has a say in it.

In the Third Dimension, in one galaxy among many, on a tiny planet among billions, two siblings stand together to face the future. Two brothers pick up where they left off, put together the pieces of their lives and reclaim something they thought they had lost. They all leave behind a town known to few, and something else even fewer dare speak of. Hidden away in the forest where the fabric of reality is at its thinnest, a hand stays stretched out in wait.

Within the stone cage, the screaming has ceased. The all-seeing eye remains closed. For the first time in a trillion years, Bill Cipher sleeps.

And dreams.

Just a little more summer.

"It is part of the martyrdom which I endure for the cause of Truth that there are seasons of mental weakness, when Cubes and Spheres flit away into the background of scarce-possible existences; when the Land of Three Dimensions seems almost as visionary as the Land of One or None; nay, when even this hard wall that bars me from my freedom, these very tablets on which I am writing, and all the substantial realities of Flatland itself, appear no better than the offspring of a diseased imagination, or the baseless fabric of a dream."
- A Square, Flatland.