Iago is an insidious and devious villain. There are many examples of this in the play, most noticeably perhaps, is his success in suggesting support and concern for Cassio whilst also systematically degenerating his character. He succeeds in doing this due to his accommodate personality and effective use of language.
Shakespeare presents Iago as a character with the ability to change his manner of speaking according to who his speech is directed. With Cassio he is blunt and genial as shown in Act II Scene three with lines such as ‘Marry, God forbid’ and ‘You have lost no reputation at all’. Whilst with Othello, his language is eloquent and sycophantic, as shown through phrases such as ‘good my lord’ and ‘I do beseech you’. This ability of Iago’s is key to his success in suggesting support and concern for Cassio whilst also destroying his character as it allows for him to keep up an appearance of ‘honest Iago’ to Cassio and all the other characters whilst slowly poisoning their 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’. And thus, the characters are unaware of the possibility that Iago could be deceiving them or manipulating them, after all, he is "Honest Iago."
When Othello breaks up the quarrel in Act II Scene three, Iago is again able to successfully misrepresent himself – ‘Have you forgot all sense of place and duty?’. This time, he pretends that he is there merely to settle the quarrel, when he is the engineer behind the whole affair. Later, Iago tells Cassio that he should plea to Desdemona for his position back – ‘Our general’s wife is now the general...confess yourself freely to her’. Cassio believes Iago ‘advises him well’ to do so when in fact this is all part of Iago’s plan to persuade Othello that Desdemona and Cassio