Emil is a young boy who lives with his butler, Sebastian, in a mansion between Nier's village and Seafront. He uses a blindfold to keep his eyes hidden, as anything he sees is turned into stone. He is introduced in the game when Nier and his party investigate what has happened to a friend that sends her letters. It is revealed that Emil did not send the letters, but instead his butler did. Emil temporarily joins with Nier, using his ability to turn anything he looks at to stone.
Later, Emil walks to Nier's village to warn the village of an impending Shade attack, and collapses due to exhaustion. A giant shade makes its way toward the village library until Nier seemingly defeats the giant monster. However, the creature separates its head from its body and makes its way into the library. Despite their efforts, the group cannot kill the beast, so they attempt to seal it away in the basement. After a confrontation with the Shadowlord, Kainé tries to keep the door to the basement shut, but is losing strength. She asks Emil to use his power to turn the door and herself to stone. Despite protests, he eventually relents and petrifies the door.
Five years later, Emil sends Nier a letter, stating he may have found a cure for his eyes and he may be able to save Kainé . The two of them find a secret entrance to a laboratory that is under Emil's mansion. In the library, they find out Emil has a sister that was the ultimate weapon. Emil was made into another weapon that can seal his sister away if she were to ever become uncontrollable. After a confrontation, Emil allows himself to be devoured by his sister, and cures his eyes, but at a cost. Emil no longer looks like a boy, instead he has transformed into his sister's weaponized form. He is ashamed of his new look, but Nier comforts him and tells him he's still Emil in his eyes.
They travel back to the village to unseal Kainé and the door. After five years, Nier is able to defeat the beast effortlessly. The group is then tasked with finding parts of a key that can lead them to the Shadowlord's castle. After all but one piece of the key is found, the group travels to the Aerie only to find out the entire town has been possessed by shades. Then a giant shade appears. Emil loses control and activates his ultimate weapon ability, which not only destroys the shade, but the entire town, killing everyone inside the village. This event traumatizes him until Nier again comforts him.
In the Shadowlord's castle, the group battles twins. After slaying one of the twins, the other is driven mad and opens up a black hole. Emil decides to sacrifice himself to save his friends. He allows himself to be sucked into the black hole. Before he dies, he's glad he had made some amazing friends, and is afraid to die. He sacrifices himself and destroys the black hole and the other twin.
In one of the additional endings, it is revealed that he is still alive, although only consisting of a head now. He states that he can't wait to see his friends again.
In Nier: Automata
Despite taking place thousands of years after the events of Nier, Emil, now reduced to only a head, appears in the game as a traveling salesman. Upon first meeting 2B and 9S, he seemingly has no memory of the events of Nier, however he will slowly begin to remember as either one gathers lunar tears. As more lunar tears are shown to him, Emil begins recollecting his past and sharing them with the two.
If the player collects five lunar tears, Emil is reminded of a special place, unlocking the elevator to the shopping center. On the other side of the elevator, Emil can be found standing among a recreation of Kaine's shack from the original near, amidst a field of lunar tears. Emil then explains that he built this recreation, and that he is actually one of many copies of Emil created by Emil. After this encounter, Emil gives the pair a sixth lunar tear and mentions that he has to leave and talk to the other Emil clones.
Following this, an optional boss comprised of several Emil clones can be fought. At the end of the fight, the clones attempt to self-destruct. If allowed to, the resulting explosion destroys the world, leading to secret ending Y, "A Head[Y] Battle". If the clones are stopped in time, the primary Emil clone passes away. While this likely means that every Emil clone is dead, the primary Emil clone was unsure of where the original Emil was, meaning he could potentially still be alive somewhere.
- There has been some minor confusion as to Emil's gender and sexuality, both due to censorship in Nier's original North American release, as well as inconsistent statements from Yoko Taro in interviews over the years.
- Originally, in a 2010 interview with Get News, series' director Yoko Taro responded to a question asking if Emil was homosexual by saying that to him, Emil is transgender. This is potentially symbolically corroborated by Emil merging with Halua during the events of Nier.
- However, in a later 2011 interview, Taro states Emil to be gay and have feelings for Nier. Taro specifically references Emil's interactions with Nier, as well as dialogue which was cut from the game's North American release in which Emil is disappointed to be told he will find a bride someday. In interviews since, Taro has consistently given this response. As well, the North American release of Nier Replicant ver. 1.22474487139 would reintroduce the originally altered dialogue.
- As a curiosity, his name comes from "Ludwig Emil Grimm", the younger brother of the Grimm brothers.