Nick

Pastor Nick (ニック司祭) is a member of a religion that worships the Walls and considers them holy.

Background
Pastor Nick claims that he lost his family as a result of addiction to Vine.

As a religious leader, Pastor Nick used his influence to oppose any modification of the walls, be it permanently sealing the gates or even mounting cannons on the top. Though he claimed it was blasphemy for humans to "maim" the wall, the real reason was to reduce the risk of workers discovering the Titans within during renovations.

Story
Pastor Nick first appears when he advocates for the execution of Eren upon the revelation of Eren's ability to transform into a Titan.

After Annie Leonhart breaks a portion of Wall Sina and exposes a Titan within, Pastor Nick appeals that it be covered up immediately to prevent sunlight from awakening it. Realizing that Pastor Nick knew the truth about the Titans within the Walls the entire time, Hange Zoë threatens him in an attempt to get him to reveal more, but he refuses.

Hange brings Pastor Nick with her to Hermiha District so he can see, with his own eyes, the suffering of the families forced to evacuate because of the suspected breach of Wall Rose. While he does not betray the secrets of his organization, he tells Hange about a girl, hiding under an assumed name, who would be able to speak about some of the secrets. Eren and the others realize Pastor Nick is speaking about Historia Reiss.

Pastor Nick is later seen with Levi and a few Military Policemen, watching as refugees flood into the town.