Let's face it, roleplaying universes have some strange places you can visit. Exalted has a humdinger called the Wyld. It's basically raw proto universe, the unmade, unshaped, whatever. And Creation is like a flat wafer reality that sits in a bubble of fluctuating stability in and endless ocean of this stuff/place/thing.
There are other Wyld like places in gaming. The Dreamscape of the mythos, The Umbra of the various World of Darkness, and Warhammer's Warp. It's unknowable to the human mind...but Exalted allows you to more or less walk right into it at your own peril.
For those that don't play Exalted the Wyld slowly warps and distorts people, things, ideas. You can walk in one day and if you are very lucky and don't disolve into the color "yes", you might, might walk about a whole lot less human than you were before. It is the taint Lunars must tattoo themselves against to prevent their own exaltations from distorting, and it is how some of the hybrid beast races came about.
But as a Storyteller, the place is a nightmare to describe travel in because it is basically an expressionist's artistic nightmare. It's a world of metaphors made real, and if/could/shouldn't bes happen.
The Deep Wyld as it is described is a rainbow whirlwind much like Limbo (gray from all it's colors) of the D&D Great Wheel. But just before you reach the endless Reality Blend-tec "will it blend" demo you find some pretty creative places.
Here are my top 5 tricks on how to describe weird Wyld-like landscapes:
1. Everything is literal - This one sounds easy but can get tricky. Any time a simile or metaphor is used, it is actually the literal use of the words. A "Hard Day's Night" is literally solidified daylight blocks floating in the sky during the night. "Like a Fish on the Line" when describing someone suddenly either causes fish to sprout from them, or they gain gills, a hook in their cheek, or other weird mixtures there in.
2. Puntastic - As painful as using puns are, they are great way to build strange things in the Wyld. As the day gets shorter you run out of Thyme...and loads of the herb show up. The Tide may turn like water flowing around on a great windmill in the sky, Someone is Bearly alive and they sprout hair and get big paws. It's lame but it works.
3. Low-Fi Reality - As you get further and further away from concrete reality everything begins to become abstract and sketchy. So a house might be crudely made, or just a solid block of wood in the rough shape of a house. Think giant monopoly pieces. People and animals might before iconic versions of themselves. Almost completely characterizations. They lack depth of design and are poor emulations.
4. Chimeric form - The one thing you want to least use is mix and match reality. Sure crystal trees sound fun but when you find the 13th version of it out there it gets boring. If you do play mix and match qualities try to keep a theme over a large area. So suddenly you have an above ground coral forest you need to fill it with flying fish, land walking lobsters and oceanic life. Maybe even weirder things like a Whale with feet, or winged squid. Being consistent with the theme of the localized weirdness is key. If they move past the local bubble of 'what if' then change it up gradually.
5. Islands of Alien - Every once and a while there needs to be a large bubble of semi-stable other. In this case it can be a totally xenobiological microverse. You can sci-fi it up with strange green animals with 3 eyes and triradial body symmetry or other shaped forms.I often look to the "new weird" like Perdido Street Station by China Mieville or similar authors. Imagine the movie Dark City but with frogs, etc. These dioramas or terrariums need to have more than just a mix or match or grainy reality. Pick a number of contradicting elements and then run them together as if it natural. You don't have to go magic techy, but you can go magical realism.
These 5 guidelines help me imagine the swirling, slowly evolving, anti-entropic beauty of the endless Wyld. It is not decaying but a grist of possibles being slowly rolled out in the borders. Fair Folk domains not withstanding, that can help players visualize the surreal world beyond Creation. Good luck!