Nile is a man of average height and build. He has short, thin, black hair that is cut shorter on the sides and back, and his eyes are dark in color. He also sports a very light mustache and goatee. He is always seen wearing the standard military uniform bearing the Military Police symbol, but also wears a red bolo tie similar to that of his fellow military commanders.
Nile prides himself on being a very rational individual. Whenever he is faced with a tough choice, he weighs all possible options and chooses the one that makes the most sense to him. He wanted to have Eren Jaeger executed, but was not blind to his usefulness like Pastor Nick was. He determined that the potential civil war within the Walls was too great a cost, especially considering the Scout Regiment could not guarantee anything about Eren. However, he relented his position when Levi brought up the fact that the Military Police would be ill equipped to deal with Eren in his Titan form. Nile is never totally committed to one way, and will change his opinion as the situation develops. A similar instance is when he questioned Erwin Smith due to him violating laws and command structure, but allowed his plan to go on since the Female Titan was already released and it would be very difficult to stop it without Erwin leading the Scout Regiment.
Nile first appears as the leader of the Military Police during the trial of Eren Jaeger. He advocates killing Eren due to the impending civil war, but he does analyze and weigh the different pros and cons of Eren before making his final decision. He recognizes that Eren's Titan powers had saved Trost District, but threaten the balance of power within human society. While mainly business and Wall Rose residents support Eren, most people of importance such as the clergy, view Eren as a danger. Thus, Nile concludes that to avoid civil war, Eren must not be allowed to live. Eren responds by calling him and his group a bunch of cowards, and Nile wants to have him killed; however, Levi interferes by beating Eren in front of everyone. Dhalis Zachary ultimately places Eren in the Scout Regiment, and Nile is displeased that he lost the trial; however, he asks Erwin Smith how the Scout Regiment intends to perform a mission to Wall Maria.
He later learns from Erwin Smith that Annie Leonhart is the Female Titan and that Wall Sina has been breached. Going by his suspicions, Nile orders Marlo Freudenberg, Hitch Dreyse, and the other members to assist the Scout Regiment in capturing Annie.