Nick’s reference is the Church of the Walls cult from the Attack on Titan manga series Attack on Titan (Japanese: 進撃の巨人, Hepburn: Shingeki no Kyojin) is a Japanese manga series written and illustrated by Hajime Isayama. It is set in a world where humanity lives inside cities surrounded by three enormous walls that protect them from the gigantic man-eating humanoids referred to as Titans; the story follows Eren Yeager, who vows to exterminate the Titans after a Titan brings about the destruction of his hometown and the death of his mother. Nick (ニック Nikku), often formally referred to as Minister Nick (ニック司祭 Nikku Shisai), was a high standing, devoted member of the Church of the Walls, a religion that worships the Walls and considers them to be holy. The Church of the Walls (壁教 Wōrukyō) is a religious organization that considers the Walls to be sacred, with a lot of religious and political power within them. Some of the church's members possess knowledge about the Walls that is hidden from the general public. After the truth about the Titans is revealed to the citizens of Paradis Island (and the later destruction of the Walls due to 'The Rumbling'), the Church of the Walls is assumed to be most likely disbanded. However, one key member is still seen serving the new Royal Government under Historia Reiss. Members of the church are referred to as "Wallists." Among them, there are a variety of different people from different places. There are also ministers who represent the Church of the Walls. An unknown number of ministers are involved in deep secrets regarding the Walls, which also includes information regarding the Titans inside the Walls and possibly even the mystery of the Titans.