Iago's impact on other characters

Othello - honesty

Iago tricks Othello into thinking that he is completely honest
Act I Scene III - Honest Iago,/ my Desdemona i must leave to thee

Othello - iago is a reluctant truth teller

When speaking to Othello, Iago acts as if he is telling the honest truth, but is reluctant to do so in case he hurts Othello. This makes Iago’s lies even more believable in Othello’s eyes because Iago rarely says the truth, but instead hints at it.

Othello - hints

Instead of telling Othello the ‘truth’, Iago drops hints at what may be happening. This allows Iago to plant the seeds of doubt in Othello’s mind without actually telling him outright what is going on. This eventually makes Othello go crazy, have a fit and ultimately kill Desdemona.

Othello - accepting Iago’s word as gospel

As the play advances, Othello begins to never even question Iago’s word, and to take everything he says as nothing but truth. Iago has successfully manipulated Othello and this is a key element of his plan. Iago is now completely in control of Othello
Act III Scene III - Iago says “O, beware my lord of jealousy! It is the green-eyed monster which doth mock the meat it feeds on.” This is a clear example of dramatic irony, as Iago is warning Othello of jealousy whilst manipulating him to become jealous of Cassio.

Cassio - drunk

Cassio’s low tolerance for alcohol makes him an easy target for Iago, who exploits this weakness in Act II, Scene III, to get him drunk. He then gets Roderigo to provoke Cassio whilst drunk, leading to a brawl and causing a scene.
Quote from Othello - “Cassio, I love thee, but never more be officer of mine.” (cassio is fired)

Iago gets cassio to talk to desdemona

Iago manipulates Cassio into seeking Desdemona's help to regain his position, knowing her involvement will fuel Othello's jealousy. Cassio, trusting Iago's motives, believes this is genuine advice, unaware that Iago is acting entirely in his own interest.

Roderigo - hopelessly in love

Roderigo is in love with Desdemona, who is impossible to have as she is completely loyal to Othello. Iago sees his hopeless love for Desdemona as a way to manipulate him.

Roderigo - money

Throughout the play, Iago takes Roderigo’s money and tells him he is giving Desdemona gifts on his behalf. Iago strings him along by keeping him hopeful. For example, when Othello marries Desdemona, he says that their marriage is temporary. Roderigo continues to give him jewels and money, believing he is making progress, but in reality, he is just Iago’s puppet. Iago convinces Roderigo to follow Othello to Cyprus, saying that Othello will die and he can swoop in and take Desdemona. To travel to Cyprus, Roderigo must sell all his possessions in Venice, leaving him completely powerless and at Iago’s mercy once he arrives there.

Roderigo - plan to kill cassio

When Roderigo confronts Iago, Iago says that Roderigo should kill Cassio, as he says Cassio is in love with Desdemona and thus stands in Roderigo’s way. Iago says this to frame Cassio’s murder as an act that benefits Roderigo, rather than an order he should blindly follow. Iago cleverly manipulates Roderigo in every step of his plan to get exactly what he wants.

Roderigo - killing

After Roderigo confronts Iago, Iago quietly marks him as expendable. In Act V Scene I, as Iago wounds Cassio, Roderigo finally sees through his deception and lies. In response, Iago kills him without hesitation and acts as if nothing happened. This reveals that Roderigo was never a friend to Iago, but just a tool discard once Roderigo figured out Iago’s true intentions. Iago used him financially, physically and then killed him off.

Emilia - long-term manipulation

Iago’s manipulation of Emilia is a slow but effective one. As his wife, Emilia seeks Iago’s approval and never questions his motives because she trusts him. Unfortunately, this makes her a prime target for Iago’s manipulation.

Emilia - controlling relationship

Emilia finds the handkerchief and knows Desdemona loves it. Despite this she gives it to Iago because she wants to please him. Iago also regularly shames Emilia in public, e.g. in Act II Scene I Iago says “would she give you so much of her lips/ As of her tongue se oft bestows on me,/ You would have enough.”