Negative Quasi-Elemental Planes

Quasi-Elemental Plane of Vacuum

  The Quasi-Elemental Plane of Vacuum was the Inner Plane at the intersection of the Elemental Plane of Air and the Negative Energy Plane. It was a place of utter emptiness.
 

Quasi-Elemental Plane of Ash

  The Quasi-Elemental Plane of Ash was the Inner Plane at the intersection of the Elemental Plane of Fire and the Negative Energy Plane. It was a place that sucked the warmth from any living creature. In most areas of this plane the ash had the consistency of hard-packed soil, though in some regions it was much less dense.
  The cooling cinders within the air of this plane sucked the warmth from not only living creatures, but from magical effects as well. This made long term spells such as heat metal and wall of fire ineffective on this plane. These cinders also gradually deteriorated the health of creatures of elemental fire and magma.
  History
  Records found inside of an abandoned citadel on the world of Oerth hint that a community of dwarves may have tried to establish a colony in this plane, though their fate was unknown.
  Notable Locations
  Citadel Cavitius: a massive skull-shaped fortress that was constructed by the Doomguard and later taken from them by Vecna, who partially repurposed the stronghold as a prison.
  Citadel of Former Flame: the home of Gazra, a creature who claimed to be the archomental of the plane, and the capital of the ash quasi-elemental empire. A variety of undead guarded the citadel including ghouls, spectres, and wraiths.
  The citadel itself was made from the very ash of this plane, carved and magically fused together, and was constantly altering its form in a gradual manner. Inside it was devoid of both heat and light. Both mundane and magical forms of illumination wouldn't function within it.
  Inhabitants
  The two most predominant sentient species on this plane were ash mephits and ash quasi-elementals. The former lived in scattered communities, while the latter had a substantial empire centered around the Citadel of Former Flame.
  There lived a roaming group of ghasts and ghouls on this plane, numbering in the hundreds, that were referred to as the Flesh Renders. Due to going great lengths of time without any sustenance, they were particularly savage undead. Some speculated that they may have once been minions of Vecna
 

Quasi-Elemental Plane of Dust

  The Quasi-Elemental Plane of Dust was the Inner Plane at the intersection of the Elemental Plane of Earth and the Negative Energy Plane. It was a place of wind, sand, and grit, where living creatures ever decayed to dust.
 

Quasi-Elemental Plane of Salt

  The Quasi-Elemental Plane of Salt was the Inner Plane at the intersection of the Elemental Plane of Water and the Negative Energy Plane. It was a place of endless thirst.
  Description
  Creatures and elementals of water, as well as creatures containing water, suffered rapid dehydration the longer they stood in this plane. This also affected elementals of water-related liquid planes, such as ice para-elementals, ooze para-elementals, and steam para-elementals.