Here's my interpretation. The song is about a man (the protagonist) who has preached all he can to a world of hate and evil, and has been heard by a deaf ear. The raven is a symbol of the omen of man's plight, which the main character was not able to avert in his lifetime. In his final hour he is being accepted into heaven as a reward for his noble attempts, but he is unsatisfied because he was unable to accomplish his goal "Through the eternal flame I travel, and the rain keeps falling..."
Here's my interpretation. The song is about a man (the protagonist) who has preached all he can to a world of hate and evil, and has been heard by a deaf ear. The raven is a symbol of the omen of man's plight, which the main character was not able to avert in his lifetime. In his final hour he is being accepted into heaven as a reward for his noble attempts, but he is unsatisfied because he was unable to accomplish his goal "Through the eternal flame I travel, and the rain keeps falling..."