The use of allusion allows an author to add meaning to the written word by using associations, "especially for the characters and events of mythology, legends, and history", in the words of a poem.
In the seventh stanza, the raven finally made its appearance, as it entered the chamber and "perched upon a bust of Pallas just above my chamber door." Pallas Athena was the Greek goddess of wisdom; there are several possible reasons for this allusion. Perhaps Poe wanted to indicate the raven's understanding of the narrator's position since it is frequently a symbol of death. Perhaps Poe is making fun of wisdom by having the bird perch on the statue representing it.
In the next stanza, the reference to "the Night's Plutonian shore" alludes to Pluto, the Roman god in charge of the underworld. Further on, the "Tempter" mentioned as a possible sender of the raven is Satan.