Einherjar

The Einherjar are an army of elite warriors that serve as the main army of Asgard, and the main warrior-class of Asgardian society. Einherjar warriors are personally trained by the ruler of Asgard and are tasked with protecting Asgard and quelling conflicts within the Nine Realms. During times without war the Einherjar mostly serve as palace guards, notably serving as guards for Odin's Vault.

Formation
The Einherjar were first seen organized under one of Asgard's first rulers, Bor, serving as protectors of the realm of Asgard under his rule.

As the kingdom of Asgard grew in influence within the Nine Realms, it took on the role of keeping the peace between the worlds of each galaxy; thus the Einherjar were further tasked with policing the Nine Realms, preventing any realm from threatening any other realm's natural way of life.

Convergence
Eons ago, during a cosmic event known as the Convergence, the Dark Elves, led by Malekith, attempted to destroy the universe using a weapon known as the Aether in a bid to return the universe to its original state of darkness. However, they were met with resistance by the armies of the Einherjar, lead by the then-current All Father, Bor.

The two sides engaged in a prolonged conflict with the Einherjar fighting the armies of the Dark Elves, including their empowered "Kursed" warriors. The Asgardian army eventually stopped Malekith, stealing the Aether from him using the Bifrost. However, a majority of the remaining Einherjar died as Malekith sacrificed his fleet of war ships, dropping them from the sky onto the warriors on the battlefield below.

Over time, Asgard rebuilt the forces of the Einherjar, who served in many more conflicts in other realms over the millennia before leadership was passed from Bor to his son, Odin, the current All Father of Asgard.

Battle against the Frost Giants
In 965 A.D. an army of Frost Giants from the world of Jotunheim invaded Tønsberg, Norway, in an attempt to subjugate Midgard (Earth) and plunge it into a new ice age using the Casket of Ancient Winters. However, they were opposed by Odin and an amassed army of Einherjar warriors, who, after a pitched war, drove the Frost Giants back into the heart of Jotunheim and took the Casket, forcing the Frost Giants into a peace agreement.

After a number of schemes set forth by Loki resulted in the destruction of the Bifrost Bridge, the realm of Asgard was isolated from the rest of the Nine Realms. Without Asgard and the Einherjar to maintain peace within the Nine Realms, the balance of power began to shift and many conflicts began to arise between various realms. Taking advantage of this conflict, a group known as the Marauders arose, attacking and looting various settlements in each realm, one by one.

Conflicts in Various Worls
Later, after Thor traveled to Midgard to stop Loki and bring him back to Asgard, Thor also returned with the Tesseract, which Heimdall was able to use to restore the Bifrost. With the Bifrost repaired, Odin dispersed the armies of the Einherjar to the different realms in order to restore peace to the Nine Realms. The Einherjar subsequently fought alongside Sif, the Warriors Three, and Thor to quell the conflicts in various worlds, most notably engaging in a prolonged conflict with the Marauders in the planet Vanaheim.

War of the Ring
When the Dark Lord Sauron returned, more than 60,000 Asgardians, led by Thor, traveled to the planet Arda along with 100,000 Humans from Midgard, and 30,000 Vanir from Vanaheim to aid the Free Nations of Middle-earth and end Sauron's plan from unleashing darkness to all living worlds (which includes the Nine Realms) in the universe.

Equipment
Einherjar soldiers are prestigious warriors whose uniform consist of ornate protective armor including: a chestplate with a high neck guard or collar, shoulder guards, gauntlets, boots, and other armor plating including a distinctive, ornate helmet. Their armor is also complemented by a fabric cape.

The Einherjar carry a small variety of weapons, the most common of which are a spear used for fighting enemies and keeping them at a distance and a sword for close range combat. Both the sword and the spear are capable of becoming energized by a form a mystical energy which enhances their cutting or piercing ability and damage to enemies. Additionally the Einherjar often carry an ornate, gold colored shield to provide protection against enemy attacks and can provide a small amount of protection against energy based weapons.