Einheriar

"Einheriar" (also spelled Einherjar) was a collective term for any army of the spirits of fallen humanoid warriors. Also known as spirit legions, einheriar were not undead; they were once-mortal petitioners specially chosen to serve in the armies of the Outer Planes, most commonly in the Upper Planes. They were numbered among the Celestials.

The term, which translated as "faithful", properly and most commonly referred to the noble warriors of Asgard,  who served Odin; however, over time, it also came to be used for the formerly mortal armies of other planes,   such as those of Arcadia or the dwarven hosts of Clangeddin Silverbeard. Some of the powers of the Faerûnian pantheon had einheriar in their service, including Ilmater. In the Netherese pantheon, both Mystryl and Tyche were served by them. Eilistraee, goddess of the good drow, also had a host of einheriar. Einheriar loyal to Indra of the Lords of Creation were also known to serve the deity in the homonymous layer of Limbo.

The word was also used in the singular to refer to an individual member of the einheriar.

Description
Einheriar were described as wispy in form, including their armor and weapons. The majority of einheriar were once human, and they still looked similar in appearance to the persons they once were in life.

Einheriar were suited in the highest quality of armor, usually with a design that hinted at the god or goddess whom they served. Rarely, their armor had minor magical enhancements.

Abilities
Einheriar were among the toughest examples of their former race. They were exceptionally fleet of foot. They also had minor resistance to magical spells,  and most were immune to fear. Sometimes, the deity who commanded the einheriar would grant them additional powers.

The greatest among them were powerful enough to be considered quasi-deities. Such individuals were impossible to polymorph and were immune to mind-affecting maladies and magics that would drain their essence or abilities. They were strongly resistant to fire, to spells, and to physical attacks from all but the most powerful of magic weapons.

Einheriar were immortal. If they were killed, they would simply return to life again after a short time to fight another day.

Personality
Einheriar were wholly obedient to the powers or proxies who commanded them, faithfully following their orders with great fervor.

Society
When encountered on the planes, einheriar could be found in patrols numbering from 10 to 100 persons, marching in military units. These patrols usually included a majority of fighters,  but other classes of warriors were among their numbers as well in smaller percentages. According to estimates as few as 10% and as many as 20% were divine spellcasters, while from only about 3% to as many as 15%  were arcane casters. These were the roles that each warrior once held in life, and each recalled the full extent of his or her training and combat skills as a mortal.

There was no hierarchy among their ranks. All einheriar were equals, subservient to their commanding power or proxy. They respected other celestial beings as aasimon and archons, but they worked independently of them. Einheriar received their instructions from the powers through prayer.

Ecology
As spiritual creatures, einheriar did not need to eat to survive.

History
Dwarven einheriar from Mount Clangeddin in Arcadia frequently entered Acheron to battle in epic array against the evil forces there.

The einheriar of Asgard resided in Odin's feasting hall of Valhalla, waiting for the great battle of Ragnarok.

Elven high mages had developed an epic spell to summon an army of einheriar to defend their homelands.