Final answer:
Iago's soliloquy uncovers his malicious intentions towards Othello, showcasing his manipulative nature and foreshadowing the tragic outcome of the play.
Step-by-step explanation:
The importance of Iago's soliloquy in Shakespeare's play reveals his true nature and plans as a character. During the soliloquy, three key facts become apparent: Iago's contempt for Othello, his manipulative and deceitful nature, and his scheme to use others, such as Roderigo and Cassio, as pawns in his plot against Othello. These revelations make it clear that Iago is the antagonist of the play, setting the stage for the tragic events that follow.