Obsidian Forest

A long time ago, a group of mercenaries decided to hunt the Witch to test their strength. They knew it was a suicidal mission, and yet they didn't care.
Somehow, they managed to kill her, but as they did, all of the Colors spilled out of her, oversaturating the woods they were in. And the Color that outbalanced every other was Black. This is how the Obsidian Forest was formed.

A giant reef

As it is common for every oversaturated area, all of the trees changed, their bark softened, so did their wood. They started to look like giant single-cell organisms with multiple, glowing nuclei the size of an apple within them. But the Black warped them further. Being the Color of strength, it filled them with vitality, making them grow to enormous sizes. While growing, some of the trees connected with each other, forming giant structures. Some started to harden again and became harder than steel. They became the structures on which the other trees could grow further. Others formed into very long, tentacles that flow with every blow of the wind, similar to some of the sea anemones. The variety of the trees growing here is so big, that the scientists researching the effects of oversaturation on living beings tend to visit Obsidian Forest once in a while. Of course, with the entourage of guides and warriors experienced in fighting with the beasts here.
Right now, the forest resembles a colossal, evergrowing, black land coral reef that glows with a slight red and purple light. The structure is partially hollow inside, forming multilevel tunnels.

Night, even during the day

Because oversaturation affects even the skies, no matter how bright it is outside, once someone enters the Obsidian Forest, it gets as dark as during the moonless night. Even the light sources brought hee tend to be way dimmer.
Even though normally it would be advised not to bring the light, as a single flame can be seen from afar in the darkness, the beasts living here already adapted to the monochromatic landscape.

Fauna

All of the animals that survived the oversaturation of their natural habitat changed. The first noticeable change is that (even if it is possible to somehow recognize what they were before) they all grew to the sizes impossible for their species. With the influence of Black, their bodies strengthened but also started to mutate faster and faster. Some of them learned to adapt quickly to any adversity, however, they got so attached to the source of their power, needing more and more of it, that they can never leave the forest anymore.

Type

Forest

Beast of obsidian forest

Beast of obsidian forest

The mercenaries who managed to kill the Witch here didn't manage to escape. Their leader, the one who dealt the final blow, got hit the worst. His body grew, horns and spikes forming on his body. He became the Hunter in the Dark, and although he lost his bow (which became a Hue Seeking Bow), he now uses spears to hunt anything that enters his forest.
His men turned either into Huntsmen or more feral Bloodhounds. Even after being warped into beasts, they all stay together and hunt together.

Dangerous weather

Even the weather here can be quite deadly. As the Black strengthens everything, it can do so to all of the atmospheric phenomenons.
The raindrops start to fall with such a strength, they can cut through leather. On sunny days, it gets incredibly hot. Wind can easily knock someone off their feet. The winters here are impossible for people to survive.