Kelemvor

Caithus stood on the highest portico of Ravenloft. The mists of Barovia parted as he beseeched his Lord to banish the curse on the Land. For a moment he beheld a figure wearing grey robes holding a scale of bone in one hand and a jagged blade in the other. Yet it was his visage that was most striking. A silver masque, expressionless and grim, beheld him - refusing to betray even the slightest hint of emotion as it judged the proceedings impartially yet turned a cold gaze onto the misdeeds of those who cheated death. 
- The Curse of Strahd
Kelemvor is, along with Lathandar and the Oroboros, one of three major gods in the Lumeric Pantheon. Like the other two, he is known by many names and his worship forms a major religion in its own right. 
Unlike his fair sister, Kelemvor is a grim god, and his depiction and purview are always the same. His is the grim countenance of death, his visage an expressionless death-masque of silver. His instruments are a jagged sword and the scales of judgement with which he weighs the spirits of the dead and guides them to the Wheel to be judged and returned to the Cycle in one form or another. Kelemvor is not the most popular god among the masses, but does have a dedicated following in parts of the Holmgardian Empire, where he is seen as a saviour against the undead. 
Just as Lathandar is associated with the sun, Kelemvor is associated with the moon, the light of which battles Sanguine's utter darkness with a silvery glow.

Holy Books & Codes

The Book of Kelemvor is a simple, undecorated tome. As is Kelemvor's preference, it describes his rites and laws in a straightforward numbered list with little pretense or flowery language.

Tenets of Faith

Kelemvor is a stern god with little desire for pomp and ceremony. His followers wear simple clothes of grey, black, and white, disdain the pursuit of pleasure, and find purpose in venerating the dead (or battling the un-dead). Above all, Kelemvorites venerate the sanctity of death and the sacred moment where a spirit is returned to the ether. Kelemvor has purview over their journey from thereon, and it is his role to judge the dead - in theory. Because of the disparate nature of religion across Erden, in practice those outside of the Lumeric Pantheon often escape Kelemvor's judgement, a fact that causes the god of death much resentment.

by Copilot

  The Orders of Kelemvor
Kelemvorites are insular and militaristic and the most zealous Kelemvorites join the Order of Kelemvor, where they train to become disciplined warriors. The bulk of the Kelemvorite legions are composed of polearm wielding acolytes, who bear halberds and glaives and fight in a tightly ordered phalanx. These units are led by Paladins, who ride panthers into battle. Chapters of the Order are found across Erden, with the most powerful being found in Carovin and Tyndis, each commanding forces of thousands. 
The result of this is that the Order of Kelemvor constitutes one of the most formidable fighting forces across Erden. Though relatively small in number, they are utterly fanatical, disciplined, and armed to the teeth with holy magic and silver artifice.