Underworld
Underworld is the realm of the dead, mostly separate from Creation. It is a whole world of its own. Its geography mirrors that of Creation.
(From Ink Monkeys:)
The Underworld is not as Creation is. It is a place of extremes: dark and bright, still and swift, elegant and terrible. It has little room for the median or the mediocre. The waters of the Underworld are a flat and perfect black, or an eerie silver. Its sands are the white of bone or chalk. Its sky is a leaden curtain by day; by night the clouds roll back, exposing a jet sheet adorned with scattered diamonds. The ornaments of the dead are spectacular: glittering blood-rubies shout out their color, demanding the eye's attention; silver crowns gleam in the pale blue light of torches that never consume themselves; ivory masks show only what their owners wish to display. Fine food weighs down the banquet tables of the dead. Grain grows straight and high like rows of spears in the Underworld's fields.
Exploration reveals that the Underworld contains countless cultures forgotten by the living world, the echoes of ancient treasures of the First Age, and the blasphemous secrets of the slain Primordials.
And in some ways, the Underworld is kinder than Creation. An Abyssal may observe an old man creaking his way down the streets of Nexus, frail of body, weak of constitution, squinting at the world through gathering cataract-clouds. A year later, the deathknight encounters the same man in the Underworld as a ghost. The ghost wears an elder's snowy beard and his eyes gleam with years of accumulated wisdom, but his step is swift and sure, his limbs strong, his gaze keen with the clarity of the dead. He will keep this visage and this strength forever. He may be reunited with his own father, and with his father's father. These are the blessings of death.
But the Underworld is a troubled place. Mortwights and Nephwracks gather in the mad tunnels of the Labyrinth. Hekatonkhires stalk remote wastes. The empires of the dead war upon one another, each demanding eternal authority over the same small patch of land. Immaculate monks and greedy gods attack the ancestor cult, cutting the dead off from living relatives. Necromancers enslave or destroy unlucky ghosts. The Deathlords spread their nihilistic dogma across the Underworld's kingdoms, corrupt its cultures, and soulforge its people.
The Underworld is beautiful. It is a place of deep passions, of cherished memories, of worship and veneration. It is a place where love and hate hold sway. It labors under the tread of tyrants and the schemes of dead titans. The dead cry out for heroes. The Abyssal Exalted may be the ones to answer.