how does revenge become an unholy prayer, and how does Othello and Iago participate in this unholy prayer?

Othello allows Iago to manipulate him into destroying the only person in the world he loved. Iago sowed the seeds of discontent within Othello's mind. Perceiving himself to be a cuckold, Othello his blinded by his rage. He cries vengeance on the only pure thing in his life.