Einherjar

"They are Einherjar! Phantoms of a sort...The Einherjar will do the bidding of whoever summons them, you see..."

- Old Hubba explaining what the Einherjar are

The Einherjar (Otherworld unit in the Japanese version) are characters from previous Fire Emblem titles that appear in Fire Emblem: Awakening.

Description
The Einherjar take the form of a card which can be used to summon a legendary hero from past Fire Emblem games. According to Old Hubba, the Einherjar replicate these spirits of heroes down to their personalities and appearance. However these spirits are nothing more than phantoms; physically appearing as these heroes, but in the end, they are not the real thing. The Einherjar are loyal to whoever summons them. However this may lead to them being hostile towards good people if summoned by evil people. These spirits can be defeated in combat, and once defeated, they revert back to their card form and can be summoned later

In Game
Einherjar appears as either SpotPass Characters or DLC characters. There are 123 different characters total, however 13 characters appear as both SpotPass and DLC, bringing there the total to 136 different Einherjar cards. The Einherjar's status screens and portraits during level ups are their official art from their respective games. In battle, all Einherjars are built from the Avatar system excluding Marth who uses Lucina as the basis for his model. Einherjar's can fall in battle if their HP reaches zero, but they can be recruited by either summoning them again via SpotPass, recruit them by completing their respective DLC chapter, or by hiring them again from the Avatar Logbook.

SpotPass
SpotPass Einherjars can be selected through the Bonus Teams menu. After selecting a character, they will be summoned onto the world map, similar to StreetPass units, Merchants, and Risen spawns. Players can interact them on the map where they can do the following:
 * 1) Hire the Einherjar for a price. The price of the unit is based on their rating. The higher their rating, the more they will cost. After hiring the SpotPass Einherjar, the player will receive 50 Renown points
 * 2) Shop from that Einherjar's shop. These shops are commonly stocked with general purpose items and weapons. Some sell rarer weapons like Spears, Fortifys, and character weapons such as Micaiah's Pyre or Eliwood's Blade.
 * 3) Battle the Einherjar. The player may engage the Einherjar and their team (up to 9 additional units) in battle. The allowed units depends upon the map, so if the battle takes place at Southtown, only 6 are allowed while the Demon's Ingle allows 13 units. If the player defeats the Einherjar's team, the player may recruit the Einherjar for free. Regardless if the Einherjar is recruited or not this way, the player will still earn 50 Renown Points, regardless of choice.

There are 12 sets of Einherjars comprising of 10 characters per set. 9 sets are based upon a singular game such as Rekka no Ken and Radiant Dawn and 2 sets originate from Genealogy of the Holy War, one for Sigurd's generation and one for Seliph's generation. Each of these 11 sets are comprised of the main lords of each game and the main human villain for each game. The remaining slots are filled by various characters from those games. The 12th and final set are 10 additional villains from across the series, though several series are represented more than once while some are not re-represented.

Shadow Dragon

 * Prince Marth
 * Caeda
 * Ogma
 * Navarre
 * Merric
 * Linde
 * Nyna
 * Minerva
 * Tiki (Shadow Dragon)
 * Gharnef
 * Camus

Gaiden

 * Alm
 * Celica
 * Clair
 * Valbar
 * Clive
 * Boey
 * Luthier
 * Nomah
 * Deen
 * Mycen

Fire Emblem: Genealogy of the Holy War - 1st Generation

 * Sigurd
 * Deirdre
 * Quan
 * Ethlyn
 * Arden
 * Ayra
 * Jamke
 * Raquesis
 * Lewyn
 * Arvis
 * Ishtar

Fire Emblem: Genealogy of the Holy War - 2nd Generation

 * Seliph
 * Julia
 * Larcei
 * Ulster
 * Arthur
 * Fee
 * Ced
 * Ares
 * Altena
 * Julius
 * Ishtar
 * Travant

Fire Emblem: Thracia 776

 * Leif
 * Finn
 * Nanna
 * Eyvel
 * Dagdar
 * Mareeta
 * Salem
 * Olwen
 * Saias
 * Raydrik

Fire Emblem: Binding Blade

 * Roy
 * Lilina
 * Wolt
 * Shanna
 * Lugh
 * Raigh
 * Cecilia
 * Sophia
 * Perceval
 * Zephiel
 * Narcian

Fire Emblem: Rekka no Ken

 * Eliwood
 * Lyn
 * Hector
 * Florina
 * Matthew
 * Serra
 * Karel
 * Nino
 * Jaffar
 * Nergal
 * Ursula
 * Lloyd
 * Linus

Fire Emblem: The Sacred Stones

 * Ephraim
 * Eirika
 * Seth
 * Moulder
 * Lute
 * Amelia
 * Innes
 * Marisa
 * L'Arachel
 * Lyon
 * Selena

Fire Emblem: Path of Radiance

 * Ike
 * Elincia
 * Titania
 * Soren
 * Mist
 * Mia
 * Zihark
 * Lucia
 * Geoffrey
 * Ashnard
 * Petrine

Fire Emblem: Radiant Dawn

 * Micaiah
 * Sothe
 * Edward
 * Leonardo
 * Brom
 * Nephenee
 * Sigrun
 * Sanaki
 * Sephiran
 * The Black Knight
 * Oliver

Fire Emblem: Shin Monshō no Nazo ~Hikari to Kage no Eiyū~

 * King Marth
 * Katarina
 * Catria
 * Norne
 * Etzel
 * Horace
 * Malice
 * Athena
 * Legion
 * Hardin

DLC Einherjar
DLC Einherjar are recruited by clearing their DLC Xenologue. 15 of the 16 DLC Einherjar received new art from third party artist or previous Fire Emblem artists. Only Eldigan did not receive new art. Eldigan, Est, and Palla are exclusive to DLC and cannot be recruited through SpotPass. The 13 other Einherjars have different skill sets than their SpotPass forms, but their stat growths are the same as their SpotPass forms.

The DLC are listed with their respective DLC recruitment Xenologues.

List of DLC Einherjar

 * Champions of Yore 1-Prince Marth
 * Champions of Yore 2-Roy
 * Champions of Yore 3-Micaiah
 * Infinite Regalia-Eldigan
 * Lost Bloodlines 1-Leif
 * Lost Bloodlines 2-Alm
 * Lost Bloodlines 3-Seliph
 * Smash Brethren 1-Elincia
 * Smash Brethren 2-Eirika
 * Smash Brethren 3-Lyndis
 * Rogues & Redeemers 1-Ephraim
 * Rogues & Redeemers 2-Cecilia
 * Rogues & Redeemers 3-Ike
 * Death's Embrace-Est
 * Five-Anna Firefight-Catria
 * Roster Rescue-Palla
 * Apotheosis-Katarina

Etymology
The term Einherjar originates from Norse Mythology. When a warrior died in battle, their soul was guided into Valhalla by the valkyries. Their purpose was to become a part of the army of the gods for the events of Ragnarök.