The Pit

"Through thousands lives and countless years, We travel this plane of doom, looking for hope and salvation, finding none" - Travels of Magradon, by Magradon, date unknown

The Pit is one of the nine major Planes of Existence. As all major planes it is attuned to the cardinal alignment, in case of the Pit it is Neutral Evil.

Creation

At the beginning there was a single world brought to existence by The Creator, that being made a group of children, Major Gods, or True Gods, one of these gods was a creation of pure malice and evil. This Being wanted to became the bring down the creator and become the Ruler of the universe. It corrupted some of the other Major Gods and struck down the creator, trapping his being forever in a mortal soul. For what It did there was a punishment, a plane was created, one that could not ever be escaped. This dimension became The Pit.
To balance the reality, there were nine major planes made, one for each of cardinal alignments.

Eons

After the Creation, Pit was just a "small" prison, but due to the Beings power it slowly expanded, over the years souls from other realms became trapped in the Pit, either being sent as a punishment by the gods, magical mishaps and such. In time the Being became so closely aligned with the Pit that it became one with it, the plane reality becoming extension of its will. During this time the Pit grew to what it is now, a dark, horrifying place, filled with monstrosities and lost souls. As a soul cannot escape this place, every time a being dies here they are recreated and reborn to live again, with all memories of pain and suffering intact, and good memories fading. This process slowly deteriorate the soul, corrupting it into the ever-suffering monsters that inhabit the plane.
For beings of Material Plane, the Pit is a true hell, in Old Empire exile into this place was the highest possible punishment.
Eons is a description of how the time passes in the Pit, as episodes that feel simultaneously like eternity and moments. It is assumed that time passes much slower in the Pit, Magradon speaks of millions of years he spent in the Pit, even through it is assumed he was exiled around 1500-2500 years ago.

After Reckoning

When the Reckoning happened a miniscule rift appeared in the fabric of Material Plane, slowly seeping energy from the Pit, this rift is located in the ruins of Exandia inside The Crater. This rift is a subject of vigorous studies by scholars, and is expected to be the source of increased power and sophistication of both shadows and hybrids.
Through this rift appeared one of the most mysterious and famous pieces of literature in existence - Travels of Magradon, a series of stories lived and recorded by titular Magradon, describing reality of the Pit, how he was sentenced for exile by Old Empire for advocating against the war with Dumari publicly, how he spend countless lives in the Pit, clinging to his sanity.

Mokai

According to Magradon, the Mokai are the only civilization of the Pit. This tribe of all possible intelligent species lives in the settlement of the same name. They survive by keeping written tradition, reminding ones that are reborn of their past lives, all things good. If this fails Mokai cleanse the corruption with the iron fist.

Type

Dimensional plane