Iago is surrounded with bitter irony: he is not as he seems, his good is bad for others, people repeatedly rely on him, and he betrays them. He likes to have others unwittingly working to serve his purposes. But for all this, as his plot against Othello starts moving and gathering momentum, he loses control of it and must take real risks to prevent it from crashing. Iago is a man with an obsession for control and power over others who has let this obsession take over his whole life. Necessity forces his hand, and, in order to destroy Othello, he must also destroy Roderigo, Emilia, Desdemona, and ultimately himself. The one man who survived Iago's attempt to kill him, Cassio, is the only major character left standing at the end of the play.
William Hazlitt wrote: "Iago is an extreme instance . . . of diseased intellectual activity, with the most perfect indifference to moral good or evil, or rather with a decided preference of the latter, because it falls more readily in with his favorite propensity, gives greater zest to his thoughts and scope to his actions. He is quite or nearly indifferent to his own fate as to that of others; he runs all risks for a trifling and doubtful advantage, and is himself the dupe and victim of ruling passion — an insatiable craving after action of the most difficult and dangerous kind."
The great nineteenth-century actor Booth wrote about playing Iago: "To portray Iago properly you must seem to be what all the characters think, and say, you are, not what the spectators know you to be; try to win even them by your sincerity. Don't act the villain, don't look it, or speak it, (by scowling and growling, I mean), but think it all the time. Be genial, sometimes jovial, always gentlemanly. Quick in motion as in thought; lithe and sinuous as a snake."
