Ironically, although Iago, near the beginning of Othello, says that he hates the Moor as much as he hates “hell-pains” (1.1.151; Signet Classic Shakespeare), he later closely identifies himself with hell. Thus, when falsely advising Roderigo later in the play, Iago says,
If sanctimony and a frail vow betwixt an erring barbarian [that is, Othello] and a supersubtle Venetian [that is, Desdemona] be not too hard for my wits, and all the tribe of hell, thou [that is, Roderigo] shall enjoy her. (1.3.349-51)
A little later in the same scene, after Roderigo has departed, Iago announces that he has thought of a way to deceive and destroy Othello:
I have’t! It is engendered! Hell and night
Must bring this monstrous birth to the world’s light. (1.3.392-93)
As is so often in the case in so many of Iago’s speeches, practically every word in the quotations just cited is ironic. Thus, when he refers to “sanctimony,” or a sacred bond, he reminds us of his own bond with Othello, which he plans to break. The words “frail vow” are ironic for the same reason. Iago, meanwhile, is in some ways much more an “erring barbarian” than Othello is; he corrupts and perverts and abuses his reason, and he is far more of a real outsider, far more of a truly uncivilized person, than Othello is. Similarly ironic is “supersubtle” – a word that applies far more to Iago than to Desdemona. Meanwhile, little is ever “too hard” for Iago’s “wits,” but he has corrupted and perverted those wits. By identifying himself with “all the tribe of hell,” Iago gives us an important clue about his own personality and motives. Likewise, when he later identifies himself with “Hell and night,” his words are revealing, and indeed some critics seem him as almost literally (not just figuratively) demonic.