Iago is malicious and manipulative. He possesses deep hatred towards all those who have wronged him and does not understand the term "love" however; he is also the clever opportunist, using every possible chance to further his plot in bringing about the downfall of Othello and unintentionally the innocent Desdemona. To say that this mastermind should be thankful entirely to fate or chance would in turn be undermining one of Shakespeare's most intriguing villains.
Iago uses his ''honest" visage throughout the play to get him where he wants to be. This honest trait, used to gain the trust of both Othello and Desdemona, ultimately leads them to their tragic downfall. The fact that Iago's knowledge of what his "honesty" can do is evidence of a manipulative schemer.
Throughout the play, there had been three distinct opportunities that have fallen Iago's way which have helped him further his plot. The three events: the dropping of Desdemona’s handkerchief at the moment which suits Iago, Cassio’s coming upon the suspicious Othello when he is in a swoon and Bianca’s arrival at just the right time for Iago to use her as the object of the conversation between him and Cassio which convinces Othello of Desdemona's adulterous affair.
These three incidents were all that "Fate" had presented to him. From there on after it was Iago who had made use of these opportunities. He used the handkerchief to poison Othello’s mind. The handkerchief being dropped, after his many pleads to his wife on stealing it, had no act of its own until exploited by Iago. His clever manipulation of this handkerchief is instrumental in the downfall of the newly married couple as it is "the ocular proof" that had convinced Othello of Desdemona's infidelity.
When Cassio becomes suspicious of Othello's "epilepsy", Iago was quick on his feet to tell him to leave...