Dreams are really freaking weird.
I have had some utterly bizarre dream experiences. Some of the weirdest have been while lucid dreaming, which was the first thing in the category of "weird quasi-scientific esoterica" that I realized was actually real when I trained myself to start doing it a teenager.
My dreams tend to be pretty wild (and often full of adventure and conflict) which I attribute to my vivid imagination and visualization in general. But like... I don't have regular work dreams. I have "fighting giant murder bears" or "imprisoned by a secret society" dreams.
I've also experienced the thing @owlsarepurple is talking about (where your body is awake but you're not yet) and have had a LOT of sleep paralysis experiences in my life to the point that it doesn't even upset me anymore because I've learned to just calm down and work my way out of it.
I know people make this observation all the time but it's always been bizarre to me how we just close our eyes and hallucinate HARD every night in completely realistic sensory states. It really makes you appreciate what your brain is capable of. And we have such rich histories of using dreams for divination, prophecy, self-understanding--whatever--in most cultures. Chaos Magic training (and I assume other schools) encourage you to develop your ability to recall your dreams as a magickal sensory aid.
When I was getting really into lucid dreaming in my 20s I was obsessed with the "actors" in my dreams for a long time. It really bothered me that there were independent people in MY dream that I didn't always have full control over, who had access to information I didn't. I call them actors because I don't really know what else to call them. That was one of my core problems I was curious about: What the hell ARE these independent entities who exist in my head even when I'm ostensibly in control of the dream and aware that I'm dreaming?
Even weirder was that they seemed to have independent emotional states and info and be able to resist control I'd tried to exert over them sometimes. Like anyone, I had a lot of fun in sexy situations when I first started playing around with this. But I noticed sometimes that I couldn't directly control the actors and that sometimes they didn't want to do that when I wanted to, which of course made me very uncomfortable with trying to force it (even though it was all my own head). I was fascinated rather than frustrated by this so in my usual ridiculous style I decided to try using my time in lucid dreams to pepper these weird pseudo-people with questions about what they were to try to understand them better.
The next time I became aware that I was dreaming I asked them directly about how they could be separate from me and who/what they were--I was given answers that didn't make sense in language and asked them to explain some other way. One of them showed me a computer and explained something about how they were the same as potential states between when it's turned on or off.
I have no idea if this was true or if some quantum nonsense had just rubbed off on me to invent this. But as I started trying to ask follow up questions, a black screen slammed down over my lucid dream and I was left floating in empty blackness with a VERY STRONG sense that someone had shut down or "unplugged" my dream somehow. Like I was exploring stuff I wasn't supposed to. I had to like... throw my consciousness at my sleeping body over and over again to wake myself up because floating in black space with nothing to do sucked. I remember all of this very vividly.
Ever since that dream (which is probably 10+ years now) the dream actors in my lucid dreams refuse to talk answer questions I throw at them and get REALLY mad at me when they "realize" that I know I'm dreaming, which I purposely conceal from them sometimes because of this. It's extremely unnerving when the weirdo pseudo-people in your dream get mad and stop interacting with you when they realize you're conscious. It creeped me out and I eventually stopped trying to lucid dream much because I didn't like it.
I didn't know what to make of this and still don't. But recently I've been reading some Jung and thinking about those experiences. Part of Jung's schtick is that symbolism is the language of dreams, and dreams are our unconscious speaking to us. My experiences with tarot have led me to believe that tarot is tapping into this same sort of "collective unconscious" space somehow that humans have access to and uses the same language of symbols to convey meaning... both tarot and dreaming are associated with divination.
So using that model, let's assume for a moment that there's some kind of like... global possibility web that contains infinite possibilities, like an ocean of of future states and information that can be tapped into (it's a metaphor, I'm not saying this exists exactly). And if humans have some innate possibility to tap into this in trance states or altered states (entheogens, meditation) it makes sense that dreaming could tap into this too (since again, you're tranced and vividly hallucinating).
This makes me wonder, again, what the hell these dream actors are, though. Because if dreams CAN be tools of prophecy/divination and actors (hypothetically) come from this collective unconscious to impart wisdom, are they the same parts of you you can't normally access? This tracks for me, and it's also interesting for me to consider in the context of the idea that different parts of our body may have their own intelligence/autonomy separate from our mental (brain) self-awareness. Which would explain why conscious, non-trance ego-oriented brain states focused on physical senses don't allow us to tap into these same sources.
Could it be that we have to be quiet enough to hear parts of ourself pierce this veil to effectively tap collective unconscious? This might also explain why @owlsarepurple had her experience of "being awake" without awakening because her brain hadn't switched modes yet even though her body had... and also provides a neat explanation for sleep paralysis which could be the reverse.
I'm also weirded out by time dilation in dreams which is markedly similar to time dilation I've experienced in entheogen states. I have absolutely had the experience of living months or weeks in my dreams when only hours have passed outside. I've always assumed this is something similar to how a computer might calculate a game state a few steps forward without rendering the intervening frames so that there's perfect information of the interim without physically experiencing it. Like experiential skipping.
But I also think it's possible that whatever part of you is brushing that collective unconscious space may not be bound by normal time at all--like if you can access some other form of knowledge outside of known physics, why should that be limited to normal time scales? This thought also makes me very uncomfortable because it suggests that if you have a bad trip and spend years in some kind of hellscape, you may ACTUALLY be spending years there.
I'm not sure it actually matters what the mechanism is, though, or how we interpret it. But I also think it's probable that not all dreams tap this space (if you're along with my model for the sake of argument)--recall that we have different sleep states involving REM and non-REM dreams. Maybe one of these brain states brushes this zone while the other doesn't? And if you think of this space as a playground of imagination in some ways, you may not bring anything useful back... which is why not all REM dreams may be divinatory.
Robert Jordan, oddly, explores some of these concepts in the Wheel of Time. He writes about Tel'aran'rhiod which is a deeper world of dreams than normal dreams which people can pass in and out of and which has more purpose and meaning than regular dreams. It's clear to me as an adult that he was influenced by some occult and lucid dreaming ideas. But this fantasy example may actually be a not-terrible model for how this could work (again, if you accept my hypothetical model). It's fascinating to think about.
Anyway, this is all HIGHLY speculative and I have no way of knowing how much any of this might be true or useful. This is a topic I intend to come back to again eventually as I go deeper on tarot experimentation and research. But I am absolutely convinced that there is something weird going on with your brain that's common to entheogens/meditation/trance/tarot/dreaming and that it does... something... that we don't fully understand. Might be self knowledge, but might be even more woo than that.
Definitely worth exploring and absolutely something I'm going to come back to eventually.