Limbo

Limbo exudes chaos at a level that is unfathomable to most beings. Sheer, unadulterated energy that cannot be controlled by any being of any power.
If a mortal being were to enter this plane, they will receive what looks like flashes of images. Peoples faces, mountain sides, words, a glass of water, a blade of grass, a loaf of bread, a goblin, and literally anything else. If the mortal is exposed to a tear, window, or if they've entered the plane itself, they will have mere seconds to escape it or go mad. The energy and sheer chaos of it all envelopes the feeble minds and too much stimuli and information entering at once can even cause death.
Stronger beings and deities can manage the vast amounts of information flooding their minds to a greater extent. It makes a great hideout because no one in the cosmos would really want to go through the effort of retrieving someone from there in the first place. While some may be able to sustain themselves in the plane and they can alter certain aspects of it, it is wildly too powerful for anyone or thing to claim dominion over it.
For those that are able to block out the flood of visions and voices, some by turning their minds into a dark void altogether, would see a desolateness world of indescribable terrain. Most of the landscape is made of what looks like chunks of earth being torn out of the ground, objects that you would expect to find in a town and things from the wilds can be found just floating around seemingly aimlessly, and great bodies of different elements drifting around. The most jarring thing for most is that your sense of depth goes almost completely away. You wouldn't be able to tell if something is very large and very far away or if something is very small but right next to your face.
The visuals, not the flashes of everything but the way you actually see, can very based on each time one visits or by the centimeter that you travel. Sometimes you may experience sight like a snake, sometimes things could look like the take on me rough sketch with pen and ink style of drawing, maybe everything would be fluid like a lava lamp floating up and down, or anything else you could or can't imagine.