In Act 2 scene 3 of Othello, Iago states his plan to manipulate the other players (Cassio, Desdemona, and Othello -- he will "enmesh them all.") There's a bit of the "divide and conquer" strategy; he's told Cassio to seek out Desdemona, so she can intercede on his behalf to restore his position with Othello (and of course, in a prior scene, it's Iago who has manipulated the situation so that Cassio is discovered drunk on watch and falls from Othello's favor in the first place.) While Cassio seeks Desdemona, Iago will plant the idea in Othello's mind that Cassio and she are having a love affair. This will enrage Othello, and causes the falling action of the play -- he murders Desdemona, who is completely innocent, and commits suicide when he learns that he's been "played" by Iago.
Iago is a liar, manipulator, and thief, destroying those with whom he comes in contact.