The predominant mood of the whole play is somber and
tragic. Iago works his evil almost from the opening scene, and each
new deception that he plans brings greater misery. The
tragic gloom that he causes is only occasionally relieved by comedy, provided by Roderigo and the Clown. The major theme of Othello is the destructive power of
jealousy. Because Othello is a totally jealous man, he easily falls prey to Iago’s plotting and scheming. His mind is poisoned by the jealousy, and it leads, both directly and indirectly, to the deaths of Desdemona, Roderigo, Emilia, and Othello. Jealousy is truly the fatal flaw of the protagonist, and the entire play revolves around it.