Einherjar Eight Warriors

The Einherjar Eight Warriors (アインヘルヤル八闘士) are a group of eight Mutos Reploids in Mega Man Zero 4.

History
The Einherjar is a task force assembled by Dr. Weil to oversee Operation Ragnarok, destroying all inhabitable areas outside Neo Arcadia to discourage anyone from running from Weil's rule.

Once the Eight Warriors are defeated, Weil transmits a message to Area Zero, proudly proclaiming that all their efforts are futile; the Einherjar were only a distraction just so Weil can finish construction on the Ragnarok space station.

Even though Weil was apparently killed during Craft's rebellion (the latter having fired Ragnarok's laser on Neo Arcadia, destroying it) the Resistance learn that Ragnarok's threat is far from over, since it's now descending to Earth. Zero enters the station one more time, and faces the resurrected Einherjar once more. Zero defeats all of them a second time before going on to face Dr. Weil himself.

Members
Under Craft's command, they were tasked with missions that would disrupt life in various ways in Area Zero.
 * Sol Titanion took control of an artificial sun. The sun's rays are amplified to nearly unbearable (even for Reploids) temperatures, turning the surroundings into a desert wasteland. Zero weakens the sun's functions by destroying its generators and shuts it down for good when he takes down Titanion herself.
 * Heat Genblem uses his own body to power a mobile particle cannon headed towards Area Zero, periodically firing devastating beams to ravage the landscape. After Zero infiltrates the weapon by going through its barrel, he destroys Genblem, which also leaves the cannon without a power source, ending its threat.
 * Popla Cocapetri infects an ancient mechanical city with a computer virus, intent on using it as a frontline base and environment destruction weapon against Area Zero by having its development program sprawling out of control. Unfortunately for him, Zero fights through the city's automated defenses and destroy the diminutive Reploid.
 * Pegasolta Eclair pilots a massive aerial fortress towards the Settlement, using acid rain to kill the plant life below. Zero invades the fortress, destroying the generators responsible for the lethal precipitation before doing the same to its Einherjar commander.
 * Mino Magnus activates a massive electromagnetic generator, creating an abnormally large and excessive magnetic field that begins to disrupt the surrounding area in attempts to destroy Area Zero's self-regulating environment technology. His plans never reach the Settlement, as Zero fights his way to the generator and destroys Magnus, stopping the waves from wreaking havoc.
 * Noble Mandrago uses plant-like nanomachines that threatens the natural wilderness by forced chemosynthesis of the soil, invoking erosion and reducing sustainability. In turn, Zero cuts through the false jungle to reach the Reploid controlling it, who he destroys in battle shortly afterwards.
 * Tech Kraken causes earthquakes with a drill-equipped submarine, threatening to demolish Area Zero and the Resistance Base. Navigating a complex maze, Zero confronts Kraken, who reveals his ulterior motive for joining the Einherjar: defeating Zero to avenge his late master, Hidden Phantom. Nonetheless, the red Reploid defeats the Zan'ei soldier, ending his part in Weil's plot.
 * Fenri Lunaedge reactivates a facility containing old, potentially dangerous experiments. Zero overcomes the security system and rogue projects on his way to the building's final chamber, where he destroys Fenri and shuts down the facility.

Etymology
In Norse mythology, the einherjar are those that have died in battle and are brought to Valhalla by valkyries. They prepare daily for the events of Ragnarök, when they will advance for an immense battle.