What is the final impact of the raven on the poet?

The poem's speaker is at first amused by the raven when it appears at his window and then comes inside to perch on the bust of Pallas Athena in his study. He becomes fascinated by its ability to talk and tries to pick its brain for answers to metaphysical questions that occupy his mind since he lost Lenore. Gradually, the enigmatic answer the raven provides, always "nevermore," frustrates the speaker and he becomes angry. The speaker orders the bird to leave his study and to return to the dark night from which it came.
The bird declines to leave, and the poet sinks into despair. He sees the shadow of the raven on the floor of his study and understands that the depression and desolation that he feels will never be lifted. The raven represents the grief from which he will never be free.