Iago is immediately introduced as the villain, and garners no sympathy from the audience. Whereas Roderigo has some kind of sense of empathy that he expresses in his love for Desdemona, justifying his ill-will toward Othello, Iago is mostly just bitter. In the very first scene, he puts down Cassio, believing that he should have been made Othello’s officer, rather than “God bless the mark! — his Moorships’s ensign.” Iago immediately expresses his resentment for Othello, for reasons with which the audience can’t immediately sympathize with, and wishes he could achieve a promotion or some kind of social mobility.
Iago is a schemer. From the beginning, it is obvious that he is sort of the “Puck,” or the “Don John,” — the chaotic element that will progress the plot and ignite its conflicts. He convinces Roderigo to yell to Brabanzio that his daughter has been married, and has left him. Roderigo, a love-stricken pawn, is like “yeah mean, I’ll totally yell at the sleeping father of the married girl I’m into from outside his window. Great idea!” And then Iago is like “yeah, and make it a really scary yell.” In this way, it is immediately obvious that Iago has a negative power over the other characters, a villainous manipulation of the sequence of events.
Iago’s instigation creates the tension of Othello with the other characters. I’m unsure if the racial undertones are as explicit or intentional as they seem, but it seems as though Brabanzio’s reaction to his Iago’s news of his daughter’s marriage is affected by Othello’s being a Moor. He immediately assumes that magic is the cause of her affection for Othello, and it completely outraged that they could be married. This is partly because she did so without the consent of her father, a very significant issue at the time. Combined with Iago’s blind resentment and repeated reference to Othello as “the Moor,” as well as other suggestive insults, it seems his being a Moor is part of the controversy.
The first act ends with a blatantly maniacal soliloquy from Iago, that presents the sort of cliffhanger, the scheme of the chaotic character. He presents his plan to exploit Othello’s liberal and trusting nature. In addition to his outwardly villainous characterization, the association of his name made it impossible for me to not hear his lines being read in the voice of Gilbert Gottfried.