Iago is the main antagonist in William Shakespeare's tragedy play Othello. He is a manipulative and scheming character who is determined to bring down the title character, Othello, by any means necessary. Iago is often referred to as an 'evil-doer' due to his malicious intentions and actions. He is a master of deception and manipulation, using his skills to manipulate the other characters in the play to achieve his own ends. He is also known for his soliloquies, which reveal his inner thoughts and motivations.