These units are first introduced in Chapter 1 where they spawn from a portal. They are officially given the name Risen in the next chapter. They are humans who were killed and reanimated into undead warriors by Grima. It is later revealed that many of the Risen that spawned in the current time actually came from the future through the portal that Grima created to prevent Lucina and the other children from altering the future. According to Brady, even wounded people can potentially become Risen. Risen usually carry little sentience, and speak in fragments rather then full sentences; however, as time passes their words become much more clearer and they can speak in full sentences without struggling in saying words. When a Risen is slain, their bodies turn into dark dust which dissipates quickly.
Risen also have human qualities to them, but it is very likely that they seem to fade as time passes. In the DLC Death's Embrace, most of the Risen thank their killers for ending their torment upon being killed. Chrom also notes that after the battle, they "sounded more human then Risen". They may also appear to have a desire to belong, as they always seem to be attacking places where groups of people like to gather, as shown in Hot-Spring Scramble.
People can also create Risen themselves. In Henry's supports with the Avatar, Henry brings back a severed Risen arm and eventually creates a large Risen army with it. Algol also has some experience with creating Risen, as he created loyal, unquestioning Risen assassins, in addition to a masterpiece of his own. How he managed to achieve this is unknown, but it is known that he had spent a lot of time doing so, as he used the temple he built to produce them and claims that he had raided a lot of villages (resulting in a lot of test subjects) to the point where he lost count of it.
In Fire Emblem Echoes: Shadows of Valentia the Risen are revealed to be created by a Thabean alchemist named Forneus, who discovered how to raise the dead as perfectly obedient soldiers using insects called thanatophages, with the masks the risen wear containing said insects which assume control of a corpse.
While Risen are composed of various human classes and are mostly male dominated, there are also female Risen that correspond to female-exclusive classes such as Pegasus Knights and Valkyries. They often wield weapons suited to their classes, the rank of which depend on the game difficulty or chapter, but they can also carry other weapons they may drop when they're defeated. There are also grunt Risen, Revenants and Entombed, that can attack with strong Claws and Talons. They are sometimes led by the more powerful Risen Chiefs (屍兵将, Shikabane Heishō lit. Corpse Soldier General in the Japanese version).
Risen may also pop up in random locations once every hour of in-game time, and disappear from those locations. Completing a chapter or paralogue can allow Risen to spawn without waiting, but they do not have a 100% chance to appear. Using a Reeking Box will spawn them at the player's location immediately, provided there is nothing else occupying that location.
Due to their random spawning pattern, the following may happen should they appear with one of the following:
- Risen and Risen: The player fights two groups of Risen at once, with the two commanders being in the spots they may spawn in individually. After defeating both groups, the player receives 3000 Gold and a random B-rank weapon or a stat boosting item.
- Risen and Merchant: A Merchant appears on the field, usually in a place close to the player's position. If the Merchant survives the skirmish, the player will receive an item from her and she will open her shop afterwards; if the Merchant does not survive, she will disappear with the Risen.
- Risen and Outrealm Team: The Outrealm team will act as your allies for the duration of the skirmish. Any casualties suffered on the team will not affect the ability to parley with them afterward unless the leader is felled, in which case the team will vanish along with the Risen.
- The Risen's name likely comes from the fact they were humans who were killed and reanimated by Grima and therefore have "risen" from death.
- Though they are officially given the name Risen in Chapter 2, selecting one with the cursor in Chapter 1 will reveal their name prematurely.
- Usually, Risen wear masks when faced in battle. However Risen Generals and Great Knights still have the Risen mask on them despite their human counterparts lacking physically visible faces.
- The Risen are briefly mentioned by Owain in Fates during his A Support with Leo.
- According to the drama cd, Risen apparently are capable of retaining some knowledge they had from before their death, as they were capable of targeting Yarne's Beaststone due to Kjelle teaching them beforehand.