In the books
In the A Song of Ice and Fire novels, Blacktyde does not have a very distinguished history. However, at the beginning of the narrative its current lord is Baelor Blacktyde, who spent eight years as a ward on the mainland after the Greyjoy Rebellion, much as Theon Greyjoy was sent as a hostage to Winterfell. Unlike Theon, Baelor Blacktyde spent his years as a ward in Oldtown in the Reach, one of the major centers of Andal culture. When Baelor returned (when he came of age, seven years ago), he was an ardent convert to the Faith of the Seven. Due to Baelor Blacktyde's household, Blacktyde is the only one of the Iron Islands with any minority to speak of who follow the Faith of the Seven instead of the Drowned God.