This outpost is the Doomguard's base of operations on the Quasielemental+Plane+of+Salt. It is a massive, sprawling complex with a 24-story square tower at its heart. Citadel Sealt has been carved directly from the material of the plane itself, making it an impressive sculpture that is both functional and artistic. The stronghold is located atop one of the tallest peaks in the Crystal Range, the border of Salt with the Negative+Energy+Plane. In this region, the plane's moisture draining effects are accelerated and the landscape is dotted with salt statues of numerous under-prepared victims. This accelerated rate of decay suits the residents of the stronghold just fine. Citadel Sealt is controlled by the Destroyers fraction, and they readily embrace the environmental conditions of the plane.
Actually, they have no choice. Roth, the tiefling Doomlord who rules the outpost, has seen to it that the fortress provides no magical protection from the draining effects of Salt. Every factioneer is on his own when it comes to surviving in this place.
While they were once the largest group, entropy has taken hold on the group now known as the Doomguard of Salt, and their numbers dwindle due to their own destructive actions. These folks believe that entropy has to be accelerated as fast as feasibly possible. They follow the vision of their missing leader, Pentar, who previously led them, and Roth, the inheritor of her legacy. While partial to accelerating natural cycles of decay, they have taken a more active role by feeding weapons and information to both sides of the Blood War in an attempt to intensify it. They also seem to believe that any Sinker that doesn’t subscribe to their view is a pale mockery of the Doomguard as it once existed. Right now, this makes their main opponent the Doomguard of the Crumbling Citadel, and they've come quite close to wiping Spragg’s faction out. Though they’re seen as dangerous maniacs by many of the other faction members, few can fault their dedication… as well as the fact that they seem to have the largest stockpile of weapons, most of which were “liberated” from the Armory of Sigil.
The Salties have thrown their weight into making sure the damage from
the Faction War never heals. Whether they’re working to support the
Blood War in faction-held locales or striking against groups like the
Harmonium directly, they seem dedicated to making sure the other
factions remain destabilized and dispersed.
The Salties are allied with an ancient being called the Deep Mother, the queen of an eel-like race called the anguillians. They have given her a variant Amulet of the planes called the Amulet of Citadel Sealt. The amulet gives its owner the ability to travel, with up to four companions, to Citadel Sealt and gives them unrestricted access to its library. The amulet resembles the Doomguard symbol cast in crystal.
The Factol's Manifesto
The Inner Planes
Planewalker.com's Planescape Campaign Setting, Chapter 3
Sea of Blood by Bruce Cordell.