Iago is not your ordinary villain. The role he plays is rather unique and complex, far from what one might expect. Iago is smart. He is an expert judge of people and their characters and uses this to his advantage. For example, he knows Roderigo is in love with Desdemona and figures that he would do anything to have her as his own. Iago says about Roderigo, "Thus do I ever make my fool my purse." [Act I, Scene III, Line 355] By playing on his hopes, Iago is able to swindle money and jewels from Roderigo, making himself a substantial profit, while using Roderigo to forward his other goals. He also thinks quick on his feet and is able to improvise whenever something unexpected occurs. When Cassio takes hold of Desdemona's hand before the arrival of the Moor Othello, Iago says, "With as little a web as this will I ensnare as great a fly as Cassio." [Act II, Scene I, Line 163] His cunning and craftiness make him a truly dastardly villain indeed.
Being as smart as he is, Iago is quick to recognize the advantages of trust and uses it as a tool to forward his purposes. Throughout the story he is commonly known as, and commonly called, "Honest Iago." He even says of himself, "I am an honest man...." [Act II, Scene III, Line 245] Trust is a very powerful emotion that is easily abused. Othello, "holds [him] well;/The better shall [Iago's] purpose work on him." [pg. 1244, Line 362] Iago is a master of abuse in this case turning people's trust in him into tools to forward his own goals. His "med'cine works! Thus credulous fools are caught...." [pg. 1284, Line 44] Iago slowly poisons people's thoughts, creating ideas in their heads without implicating himself. "And what's he then that says I play the villain, when this advice is free I give, and honest," [Act II, Scene III, Line 299] says Iago, the master of deception. And thus, people rarely stop to consider the possibility that old Iago could be deceiving them or manipulating them, after all, he is "Honest Iago."
Iago makes a fool out of Roderigo. In fact, the play starts out with Iago having already taken advantage of him. Roderigo remarks, "That thou, Iago, who hast had my purse as if the strings were thine." [Act I, Scene I, Line 2] Throughout the play, Iago leads Roderigo by the collar professing that he "hate(s) the Moor" [Act I, Scene III, Line 344] and telling Roderigo to "make money" [Act I, Scene III, Line 339] so that he can give gifts to Desdemona to win her over. During the whole play however, Iago is just taking those gifts that Roderigo intends for Desdemona and keeps them for himself. Roderigo eventually starts to question Iago's honesty, saying "I think it is scurvy, and begin to find myself fopped in it." [Act IV, Scene II, Line 189] When faced with this accusation, Iago simply offers that killing Cassio will aid his cause and Roderigo blindly falls for it, hook, line, and sinker. "I have no great devotion to the deed, and yet he has given me satisfying reason," [Act V, Scene I, Line 8] says the fool Roderigo. And with this deed, Roderigo is lead to his death by the hands of none other than, "Honest Iago."
Cassio, like Roderigo, follows Iago blindly, thinking the whole time that Iago is trying to help him. And during this whole time, Iago is planning the demise of Cassio, his supposed friend. On the night of Cassio's watch, Iago convinces him to take another drink, knowing very well that it will make him very drunk. Cassio just follows along, though he says, "I'll do't, but it dislikes me." [Act II, Scene III, Line 37] Iago is able to make him defy his own reasoning to take another drink! Crafty, is this Iago. When Roderigo follows through with the plan Iago has set on him, Cassio is made to look like an irresponsible fool, resulting in his termination as lieutenant. After this incident, Iago sets another of his plans in motion by telling Cassio to beg Desdemona to help his cause, saying, "she holds it a vice in her goodness not to do more than she is requested." [Act II, Scene III, Line 287] And thus, Cassio is set on a dark path which leads to trouble and mischief. Yet, Cassio follows it blindly telling Iago, "You advise me well." [Act II, Scene III, Line 292] With this, Cassio is eventually led into a trap where Roderigo maims him, and all that time, Iago - his friend - is behind it all.
Lowly Iago, is capable of anything - not even Othello is safe from this villain. Othello holds Iago to be his close friend and advisor. He believes Iago to be a person, "of exceeding honesty, [who] knows all qualities, with learned spirit of human dealings." [Act III, Scene III, Line 257] Yes, he does know all about human dealings, but no he is not honest. He uses the trust Othello puts in him to turn Othello eventually into a jealous man, looking everywhere.