How do these details in "The Raven" relate to the narrator's assumption that the raven is an agent of the supernatural?
The first stanza presents a speaker who is physically exhausted and under emotional strain. He reads to distract himself from the sorrow, but the "quaint and curious volume of forgotten lore"
implies a taste for the occult or the fantastic.
The fact that the narrator has been reading an old tome about the supernatural world suggests his frame of mind at the beginning of the poem. It also suggests the depth of his grief. He seems to have turned to the supernatural in an attempt to reach Lenore who has been lost to him in this world. His reading has taken him away from reality, and it is in this frame of mind that he encounters the raven that appears out of the dark night.
He does not immediately make a connection between the bird and the other world, however. At first he attempts to find a rational explanation for the raven and the repetition of his one-word vocabulary. The narrator's hold on reality does not last long, though. Soon his grief overwhelms him; he descends into irrationality and despair and only then concludes that the raven is the messenger from the supernatural world. It is the place where Lenore will continue to abide, forever lost to him.