Protestants made up five percent of the population of the still relatively young Republic, and of this number only a fraction—‘Horse Protestants,’ as Catholic Ireland derisively called them—still managed to cling on to their estates and live more or less as they had done in the days before independence.
-- Narration (chapter 1)

Importance: This passage highlights some of the important social dynamics that underpin the novel. For example, Strafford and the Osbornes are Protestants, making them minorities among Ireland's Catholic majority. Additionally, the Osbornes are even more peculiar due to that fact that they are wealthy protestants who have maintained their wealth in Catholic-dominated Ireland.

Something had been niggling at [Strafford], and suddenly now he realized what it was. No one was crying.
-- Narration (chapter 5)

Importance: After Strafford first meets the Osbornes, he finds it odd that none of the Osbornes appear to be visibly devastated by Lawless' death. This fact foreshadows later revelations about...