Come, you spirits
That tend on mortal thoughts! unsex me here,
And fill me from the crown to the toe top full
Of direst cruelty; make thick my blood,
Stop up the access and passage to remorse,
That no compunctious visitings of nature
Shake my fell purpose.

– William Shakespeare

Macbeth, Act 1, Scene 5. This soliloquy spoken by Lady Macbeth after reading her husband’s letter is one of the most famous quotes in the play. The passage is an elaborate extended metaphor. Lady Macbeth appeals to the evil spirits from hell to fill her with cruelty and to metaphorically thicken her blood. She wants to block the flow of natural feelings of conscience and remorse, so that she can carry out the unthinkable deed of murdering the king. Calling on the spirits to strip her of her femininity and compassion, she desires to be transformed into the stereotypical ruthless male. Her ambition for power has set her on a course for evil.