Iago is an ancient (ensign) serving Othello, a battle-hardened veteran of 28 whose bluff honesty leaves him trusted and even liked by all who meet him.
He is obsessed with the grubbiness of sex, to which he reduces all love, and is haunted by the thought that his wife Emilia has betrayed him with his general, Othello. He hates the latter, who has chosen an academically-trained man to be his lieutenant instead of the battle-hardened Iago. He is a master manipulator, managing to play people like puppets with ease, using his blunt honesty to convince them of what he chooses. He is also a brilliant improviser, setting his plot against Othello without having thought it fully through but able to use every occasion and person he meets to further his purpose. He can change his manner instantly depending on what’s required, whether it’s spewing filth to rouse Brabantio, trading witticisms with Desdemona, openly confessing his dissimulations to his gull Roderigo, or tentatively suggesting to Othello that he look to his wife. He is a misogynist, an abusive husband, and a racist. He leads Roderigo on for the sake of getting the latter’s money, and manages to use him as an agent to cause the disruptions required for Iago’s plot. Though he originally plans to find a way to sleep with Desdemona to repay Othello for having (as he thinks) slept with Emilia, this idea soon graduates to the full plan of having the Moor murder his wife while Iago takes care of murdering Cassio. His improvisation only fails when he makes the fatal mistake of sending Emilia to tell Othello and Desdemona of the attack on Cassio, something he could hardly fail to do. He refuses to offer any explanation for his actions when he is found out and caught.