What sort of person is Iago, as he appears in act 1?

The key to Iago's character is in the line "I am not what I am"; Roderigo should take this as a warning, but fails to. Everything which Iago presents himself as is a false show; even here, he pretends to be less evil than he truly is, though this first scene represents the peak of Iago's honesty about himself with another character.