Pluton

The lowest layer of Hades is Pluton, a gloom of endless gray sand dunes, rocky outcroppings, and sparse fields of night-black poplar trees. Here the graying effect of the plane also leeches out memories, robbing visitors of their life experiences, and the landscape reflects this property. Everything looks the same and few landmarks stand out to help travelers navigate. The dangers of the gloom are enough to deter most from visiting willingly.

Geography

Dreaming Bones

Herds of nightmares thunder across the landscape of Hades. They are common on @Oinos, rare on Niflheim, and almost never seen on Pluton. The only time an unaccompanied nightmare has been seen in the gray sands of Pluton it has been on a pilgrimage to the Dreaming Bones, a great mountain in a sandy valley completely comprised of bones – the bones of nightmares.
Nightmares come to the Dreaming Bones to end their physical form, but that is not death for them. They are reborn after giving themselves over to the grisly pile, reemerging somewhere on Hades with new life and vigor. The Nightmare Princesses are the only ones that know the exact location of the Dreaming Bones so in order to die and be reborn, a nightmare must seek out one of these powerful but fickle individuals and request the location. Most of the time, the Nightmare Princesses oblige, and if the whim strikes they may send an honor guard on the trip – or accompany the nightmare themselves.
It is said that the Nightmare Princesses must rejuvenate their own bodies at the Dreaming Bones every so often, but their rebirth is different. They die as Nightmare Princesses but return as regular nightmares, and in the cosmic scales another nightmare on Hades is chosen to be elevated.

Features

Pluton Memory Leech

The gray sands of Pluton are vast, endless, and supremely boring. Every sand dune looks like the last sand dune, and the horizon blends nearly perfectly into the sky to create a featureless gray haze in all directions. The stunning dullness of Pluton on the surface hides the insidious power of the layer, which steals away memories from travelers. After every long rest on Pluton, creatures must succeed on a DC 15 Intelligence saving throw. On a failure, they lose memories dear to them – friends and family are forgotten, hometowns hold no special meaning, and even the reason for coming becomes vague and undefined. After a creature has failed four of these saving throws they lose all memories.
It is possible to restore lost memories. They return on their own, slowly regenerating, over a period of time based on how many failures the victim accumulated. Memories lost over one failure come back after 1 day outside of Pluton, while two failures require 1 week and three failures require 1 month. If a creature that has failed four saving throws can somehow be directed outside of Pluton, they remain memoryless for 1 year.