Note: This takes place in the same night as the previous two chapters.

Eyes snapping open quickly, he was mildly surprised that the sleepiness wasn't clinging to his eyelids and begging him to return to his peaceful slumber. Sitting up on his uncomfortable mattress – which he didn't fail to notice seemed more torn up than usual, - he glanced around his sharp surroundings. In his bedroom, it was darker than he remembered and it wasn't because of the time of day; there wasn't a sun nor a moon outside, no trees of grass or anything: just an empty black void. The room itself was cast in an ominous dark shadow that ate at everything: the floorboards; the bed; the shelves. Even Mabel's posters - despite being their same bright pinks and blues – seemed less cheerful in the dank room. Cobwebs adorned the corners of the room and filled cracks in the walls, but were vacant of the arachnids that usually accompanied them. Slipping off of the creaky bed, he noticed that he was fully clothed, clad in his day clothes, cap and shoes included and his mind went back to the dream in which he'd met Bill. Was he dreaming again? Padding over to the crooked door which was hanging on by a single hinge, he opened it and looked out: instead of the room he was usually greeted by, there was a black void much like the one outside of his window. Leaning over, he glanced down and peered into the void; it appeared to be bottomless. He went back in and closed the squeaky door. "Bill?" he asked, looking around for the familiar triangular shape of the demon.

A bright flash filled the corner of the room, next to Mabel's bed and left multi-coloured splodges once it had lessened. Instead of the dream demon the boy had been expecting, there stood a tall man. Clad in a white button-up shirt and a blue tie, he donned a beige trench coat, a pair of black trousers and black dress shoes. His chocolate hair was short and mildly scruffy, blue eyes pierced the air and stared directly at the teenager.
"Who are you?" Dipper asked warily, stepping back.
"My name is Castiel and I am a dream angel," the man – Castiel – replied. His voice was a dull and low monotone that sounded uninterested in the subject.
"A dream angel?" the teen's brows furrowed.
"Yes, I don't have much time to talk to you so listen well, Dipper."
"How do you know my name?"
Castiel ignored the question; "your deal with Bill Cipher, the dream demon, must be terminated."
"Why?"
"Your world is in grave danger; he plans to start the apocalypse once he has obtained a vessel – a physical form."
"What are you talking about? What apocalypse? Bill wouldn't do that, and honestly probably couldn't. He's a dream demon, but even he has his limits," Dipper defended.
"No, Weirdmageddon. If he gets a physical form, he will start it and you won't be able to stop it. He will kill everyone and anyone he wants to; he is using you."
"H- he isn't. You're lying, stop it," the boy denied.
The man sighed. "Alright then, perhaps I should appeal to your natural human selfishness instead," he muttered to himself. "Your mindscape. Look around it," he instructed and the boy did, glancing around the room carefully. "Surely you've noticed how dark it is, not to mention the black void surrounding this single room."
"I thought the void was normal…"
"No. It's a side effect from your deal with Bill Cipher; your mindscape has slowly been deteriorated and broken down to this single point just because of his presence."
"What?" he clutched his head in a panic, "what does that mean? I don't feel any different, how bad is it?"

Castiel opened his mouth to speak but stopped when another golden flash engulfed the room to reveal Bill wearing an irritated expression. Glaring at Castiel, he spoke to the boy: "hey there, Pine Tree. What y' up to?" despite the lightness of the words, his tone was flat and clearly not amused.
"Bill, what was he talking about?" Dipper asked. "What's happening to my mindscape?"
"Nothing you need to worry about. All of the things this guy has said is a lie, kid. Don't believe him." He looked at the thirteen-year-old. "Trust me."
The boy glanced between each being, unable to figure out who he should believe. 'What if Bill is doing something to my mind?' his thoughts echoed in the room for them all to hear.
"Pine Tree, don't listen to him," Bill snapped. "Do you really think I'm capable of starting an apocalypse?"
"Don't listen to him, Dipper. He's lying, he's using you." Castiel announced.
'But what if Bill is right? What if Castiel isn't an angel, he could be another monster trying to mess with me,' the thought echoed through the mindscape again.
"Dipper, listen to me…" Castiel said.
"Pine Tree, are you really going to trust him? This stranger? You don't know…"
The two immortals continued to talk over each other, both trying to persuade the boy. He wanted to run and hide, to not have to deal with this mess and let someone else handle it. "I…" he stepped back again and his back hit against the crooked door, unsure of what to say.
Bill stopped talking for a moment and Castiel's own pleas could finally be heard clearly; "-if not for the world then at least for your own-" before he could finish the sentence, Bill snapped his fingers and the man disintegrated in a split second.

His entire being vanished in a puff of grey ash.

"What did you do to him?" Dipper asked worriedly.
"I sent him out of your mindscape. Don't worry, he isn't dead. Unfortunately," Bill replied.
"What was he talking about when he said about the apocalypse?" the boy asked.
"Nonsense. He was trying to make you break our deal, he was lying. Like you said, I'm a dream demon. I can't start an entire apocalypse by myself."
"Then what about the mindscape thing? And it deteriorating?"
"Calm down, nothing is wrong with your mindscape. You won't go insane, or stop dreaming, or anything like that. You don't even notice it, really."
"But what's actually happening?"
"Your mindscape is just adjusting to my presence, that's all." Despite the demon's reassurance, he could see the distrust clouding the boy's amber eyes. The teen lowered his head and fiddled with his own fingers. "Pine Tree," Bill said but the other paid no mind, only continued to stare at the floor. "Pine Tree, look at me," he snapped angrily and the brunet listened this time, head rising quickly to look into the demon's eye. "Do you still trust me?"
The boy nodded hesitantly. Bill knew he was lying.

Weaving golden strands of magic around the room, it seemed to darken slightly with each moment that passed; Dipper watched for only a second before losing balance and stumbling backward, clutching his own dizzied head. The immortal watched the boy intently, golden orb locked on the human's small figure. After a long minute of silence and once the demon had pulled back his magical influence on the human's mind, he snapped his fingers again.

Dipper jolted up in his own warm bed, sweaty, panting and covers tangled around his legs. Wiping the sweat from his forehead, he glanced around the room; Mabel was in her bed and the moon outside illuminated the clean expanse of their shared room. He noticed the familiar pressure in the back of his head; "Bill?" he whispered.
'Sorry, Pine Tree. You were having a bad dream so I was going to sort it out for you, but you just woke up before I could,' the demon lied.
'Oh. Thanks,' he thought back.
'No problem. Go back to sleep, kid.'
Dipper hummed his acknowledgement.
'Oh and Pine Tree?'
He hummed again to show he was listening.
'Do you still trust me?'
'What kind a question is that?' he closed his eyes and laid down in his warm bed again, smiling. 'Of course I do.' He welcomed an oblivious slumber once more. He had no recollection of the dream.

Have two uploads together because I wanted Castiel to have his own chapter. (Sorry I had to put him in there.)
If you're curious about what he looks like just google search 'Castiel Supernatural' cause yes, he's based on a real character. But I didn't bother trying with his speech patterns...

Anyways; this chapter's plan:

So basically Pine Boy (Dipser) is gonna wake up in his bedroom except it's not really his bedroom it's his mindscape. He looks around and is like "The hell happened in here, mofo?" cause everything is all weird and creepy and stuff. He doesn't know it's the mindscape until some guy shows up – Jesus. Nah, it's not Jesus, but it's a dream angel! (Shocking, I know. Now be quiet and read on.) Let's just make up how this dream angel is going to look once I start writing, we'll also think of a name then. (Maybe it'll be Castiel? Ha, I'm sticking with that actually.) So Dipper's gonna be like: "Who is U?"
Castiel is gon say: "I is an angel and I has come 2 steal yo soul m9. Nah, jk- I'm hear 2 warn U of that mofo, Bill."
"Bill ain't a mofo, mofo. He's my man, and we gon has 69 children someday. Except not really, this isn't a porno fic." That's what Dipper's gonna say.
"Stahp braking the 4th wall, U dumb-dumb," says Castiel.
"Lol, k." Says Dipper.
Then Cassy-L is gonna tell Dipper-loo about Bill's plans with weirdmagedon or however the hell you spell it. (Google to the rescue!)
Dipper's gon be like, "nah Bill is a cool dude, man. He wouldn't try to end the world, even if he was given super powers like- oh wait he already has super powers and magic, never mind. But I trust him." And let's imagine Pine boy pulling a really weird kinda 'I'm-in-love-omg-I-never-saw-it-coming-but-the-readers-did-damnit' face. That's a face now, of course – inspired by anime and manga everywhere.
Then Cas is like: "why is U humunz so dumb, always making deals with demons. If U won't listen to me, maybe you'll listen to GANDALF THE WHITE!" and Gandalf shows up out of nowhere.
(Let's just delete that bit from the actual story…)
Then while Cas is still explaining stuff, Bill can show up out of nowhere like: "We'll meet again some sunny day~" (Too soon? I'm so sorry.) he can actually be dancing to that bang bang song by Nicki Minaj or whatever. ("Bang bang into the room!")
So Bill will be like: "Coconut head, don't listen to Castiel! He iz an evil person and cannot be trusted."
Things start getting dramatic when Billzy and Cassy start arguing like an old married couple but then Bill's like "haha, I don't even care," and burns poor Castiel. (Don't worry, he isn't dead. He just isn't in Dipper's mindscape anymore!)
So Bill does the whole tappy-tappy thingy – no not tap dancing – and Dipper's like "Yeah ok, I believe you Bill xxx" with the kisses, too.
Then he wakes up and doesn't even remember the dream at all so he just assumes it was a nightmare.

End of chapter x

This was a request by a guest I think, so thanks for that. Sorry it took so long.

Thanks for reading, review, favourite, etc if you liked this chapter and haven't done so already ;D