Eld Jinn was an elite soldier in the Survey Corps. He was hand-picked by Captain Levi and included in the Special Operations Squad of which he was second-in-command.
Eld had long blond hair which had a middle parting and a bun folded at the back to keep his hair tied. He also had a small beard. Like most other Survey Corps members, he wore a green cloak with The Wings of Freedom emblem on the back. He wore the same uniform as the other Corps soldiers.
Eld was a responsible and firm leader with a strong sense of duty. He did not talk much, but when he did, he spoke bluntly and in a straightforward manner. He also seemed to have been a veteran of sorts as he teased Petra Ral and Oluo Bozado about having wet their pants on their first expedition, and sarcastically referred to them as "fine fearless soldiers." He also seemed to hold some sort of belief of what makes a true soldier, as he lectured Oluo that a kill record alone does not make a great soldier.
Appearance: Eld had long blond hair which had a middle parting and a bun folded at the back to keep his hair tied. He also had a small beard.
Personality: Eld was a responsible and firm leader with a strong sense of duty. He did not talk much, but when he did, he spoke bluntly and in a straightforward manner.
Eld Jinn in the story: After the post-Trost District battle trial to decide Eren Yeager's fate concludes with Eren joining the Survey Corps, the Special Operations Squad, is assigned to look after Eren. Eld, along with the rest of the squad, accompanies Eren to the former HQ of the Survey Corps, which will now serve as a hideout for Eren. After their arrival, Eld and Gunther notice that the HQ has not been properly maintained due to being unused.
How Eld Jinn echoes later: While speaking to Historia underneath the Reiss Chapel, Eren mentions Eld as one of the victims he and Grisha Yeager are responsible for killing by stealing the Titan's power. Later during the Battle of Shiganshina District, as Erwin Smith begins to lament the dwindling hopes of his dream, Eld stands among the many fallen Survey Corps soldiers in Erwin's mind, wanting to know if their deaths had meaning. In the forest, as Levi contemplates all the times he risked his life to save Eren, Eld appears among the comrades he had lost along the way.
Source: Attack on Titan Wiki, available under CC BY-SA 3.0.