Hades

The Gray Wastes of Hades is the Neutral Evil plane in the Dungeons & Dragons great wheel cosmology.

Its favourable location of equal "subjective" distance between the Abyss and Hell make it the most active battle-zone in the Blood War, where Demons and Devils clash over who is the most evil. Unfortunately this distracts from what Hades is all about.

It is the inverse of Elysium, being the place of ultimate evil in the existence. Worse perhaps than the Abyss or Baator if only because it is not subject to the capricious whimsy of Chaos or the restrictions of Law. Therefore it is a bleak place of suffering and misery.

Layers

Like Elysium, Hades has an all pervading aura that causes visitors to be ensnared by its nature. In this case the removal of anything joyous or worthwhile.

By merely stepping onto the plane, non-evil individuals will be subjected to harsh penalties to their mental faculties, which makes colours appear duller and sounds seem more muted. Emotions seem more alien, and visitors find themselves less empathetic or caring than they used to be.

Not only that, but the plane is also home to a unique malady known as "The Grays", which affects all visitors, including evil ones and even if they are outsiders. This steadily causes those afflicted to lose their mental faculties for every day spent abroad in Hades as they become more detached from reality and hope. In rules terms this forces their wisdom score to drop for each failed attempt to resist the condition, bringing their ability to think ever downwards until they lose their sensibilities altogether and go mad. Of course this is more dangerous for non-evil people since their senses have already been assaulted by the bleak nature of the plane, meaning they are more likely to be overcome unless they have wills of steel. The only immunity is offered to those who have high enough levels of spell resistance. However the cure is simple: get them away from Hades and their madness clears itself naturally.

The last defence of the plane is its entrapping nature, with every week spent on the plane slowly bringing visitors down to its level. This is the plane exerting itself on the better natures of mortals (Outsiders such as Demons and Devils are immune). Making them forget happy memories, or distorting their feelings into something twisted and spiteful. This of course is coupled with the influence the plane has on the senses and the affliction of the Grays, meaning the minds of people who come here will eventually crack. Eventually they forget what it means to have hope and joy and they become trapped in the plane, unwilling to leave and are more likely to descend further into madness if the Grays has not gripped them already.

As for the plane itself; it fits its nature quite well. Despite the fact that sounds and colours are already drained... there simply is no colour, the sky is grey, the dirt is grey, and the inhabitants and structures tend to the gunmetal ranges.

There is no sun, moon or stars, just an impenetrable grey sky that goes on forever.

Oinos

The first layer (also referred to as a "Gloom") is pretty much a wasteland. There is not much here other than craters, the occasional husk of a tree, the forgotten detritus of ancient wars.

Oinos is the stage of the Blood War, and thus you don't want to roam here too often, otherwise you'll find yourself running into Demons or Devils or worse.

But not only that, you'll have to look out for the Yugoloths, the Neutral evil faction of outsiders much like Devils and Demons. The seat of the Yugoloths power rests in Oinos, where there is a tower, twenty miles high called the Khin-Oin. The tower is said to be the spinal column of a long dead god that came to rest on the plane. At the top of the tower is a throne, called the Siege Malicious where the ruler of the Yugoloth species may sit. This throne also gives the user the ability to create or modify any disease with just a thought. It comes with its own price, as any ruler who sits on the throne is caused to have their skin slough off and disfiguring them. But this is nothing compared to usurpers who sit on the throne without the right to do so, who are inflicted with a particularly severe case of the gray wasting.

It is often said that Oinos is the origin source for all disease in the multiverse. So you don't only have to watch out for the Grays and the spiritual weakening that comes with Hades, but you'll also have to prepare for the smorgasbord of pestilence and corruption that exists on this layer as well.