What fills the narrator heart with terror in stanza 3 raven?

In the third stanza of Edgar Allan Poe's "The Raven," the narrator's heart is filled with terror because the raven, perched upon the bust of Pallas, utters the single word "Nevermore" in response to his question about the possibility of meeting Lenore in heaven.

This response, echoing the grim reality of Lenore's death and the narrator's desperate hope for a reunion, reinforces the narrator's despair and solidifies the raven's role as a harbinger of sorrow. The single word, "Nevermore," becomes a haunting reminder of the finality of death and the impossibility of escaping his grief. The repetition of the word and the raven's ominous presence amplifies the narrator's terror and foreshadows the lasting torment he will endure.