Nathaniel was active in his local church in Triscot for most of his life, and he was well-liked by that church's parishioners. A sociable man with a quick wit and a love of games including both Chess, and various card games (at which he is said- without malice- to sometimes cheat). He rose to the level of vice-bishop in 895, under Bishop Kellan. Nathaniel's many friends in the community included the family of Adam of Triscot, and it was to Nathaniel that Adam first suggested his old friend Toros as a replacement for Kellan, when the bishop moved to another village, in 897.
In 902, Bishop Toros joined the Protestant Movement, as did a number of spirit-talkers in Triscot (and other villages). Nathaniel was not initially among those who defected from The Order, though he did sympathize. He had no interest in choosing sides in the matter. However, when Therman (the founder of the Movement), and later Toros were killed in 903, during the Coming of the Order, Nathaniel began to think more seriously about his position, and soon converted to Protestantism. It wasn't until sometime in Las'mo' of that year (after the end of the war) that the Protestants of Triscot chose a new bishop for their village. And though Nathaniel hadn't been a Protestant for long, he was the most popular choice (in part because most other Protestant vice-bishops had died during the war).
In 904, when the surname law was passed, Nathaniel chose the name "Rook" for himself. The explanation he gave is that it refers to a piece in the game of Chess, as does "Bishop." However, it can also refer to someone who cheats at cards, and this is a habit of his which he has never denied.
In 912, Adam's clan came out of hiding (having been thought dead since the Battle of Triscot). This included Spivin Protestant, and there were rumors that Nathaniel and Spivin may have secretly been in communication, throughout the years his clan had been underground. Spivin himself had been active in the church prior to the war, and had been one of those who joined Toros in the Protestant Movement, early on. Now that they had rejoined society, Nathaniel made Spivin a vice-bishop, and there are many who expect him to someday replace Nathaniel as Triscot's Protestant Bishop.