Figurative Language

Iago doesn't literally tells us what he plans to do but rather describes it.

IAGO:

And what's he then that says I play the villain,
When this advice is free I give, and honest,
Probal to thinking, and indeed the course
To win the Moor again? For 'tis most easy
Th' inclining Desdemona to subdue
In any honest suit; she's framed as fruitful
As the free elements. And then for her
To win the Moor--were't to renounce his baptism,
All seals and symbols of redeemed sin--
His soul is so enfettered to her love,
That she may make, unmake, do what she list,
Even as her appetite shall play the god
With his weak function. How am I then a villain
To counsel Cassio to this parallel course,
Directly to his good? Divinity of hell!
When devils will the blackest sins put on,
They do suggest at first with heavenly shows,
As I do now. For whiles this honest fool
Plies Desdemona to repair his fortune,
And she for him pleads strongly to the Moor,
I'll pour this pestilence into his ear:
That she repeals him for her body's lust;
And by how much she strives to do him good,
She shall undo her credit with the Moor.
So will I turn her virtue into pitch,
And out of her own goodness make the net
That shall enmesh them all.

Act 2, Scene 3, lines 336-362)