In William Shakespeare's Macbeth, Lady Macbeth has a great deal to say, especially to her husband, about wresting power (and the throne) from Duncan, and holding on to it...at least at the beginning.
Act One is a good place to start, with scene five. First Lady Macbeth receives news in her husband's letter which reports all that has transpired, especially his "promotions" and the witches' prophecies.
Lady Macbeth is quick to understand what possibilities may be open to them if Macbeth is going to be king, but realizes that Macbeth may not have a dark enough "soul" to carry out the deed: killing Duncan— ("...All that impedes thee from the golden round [crown]...").
Her intent is clear:
Yet do I fear thy nature; / It is too full o' the milk of human kindness / To catch the nearest way. Thou wouldst be great; / Art not without ambition, but without / The illness should attend it...Hie thee hither, / That I may pour my spirits in thine ear, / And chastise with the valor of my tongue / All that impedes thee from the golden round..." (lines 11-14, 20-23)
Lady Macbeth wishes her husband home quickly so that she may work on him, poison his thoughts, so that he will be strong enough to seize this opportunity to be the King of Scotland.
When Lady Macbeth learns of Duncan's impending arrival at their castle, she calls on dark spirits to make her less soft and womanly, and harder, like a man, in order to carry out what she must, to see the murder done:
Come, you spirits / That tend on mortal thoughts, unsex me here, / And fill me from the crown to the toe topfull / 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, or keep peace between the effect and it! Come to my woman's breats, And take my milk for gall, you murdering ministers...Come, thick night, / And pall thee in the dunnest smoke of hell, / That my keen knife see not the wound it makes, / Nor Heaven peep through the blanket of the dark, / To cry "Hold, hold! (lines 35-43, 45-49)
Lady Macbeth gives Macbeth pointers as to how to hide his intent:
Your face, my thane, is a book where men / May read strange matters...bear welcome in your eye, / Your hand, your tongue; look like the innocent flower, / But be the serpent under 't. (lines 57-61)
In scene seven, Macbeth begins to have misgivings. Lady Macbeth insults his manhood and his bravery, telling him what she would be willing to do in order to achieve their ends:
I have given suck, and know / How tender 'tis to love the babe that milks me; / I would, while it was smiling in my face, / Have plucked my nipple from his boneless gums, / And dashed the brains out, had I so sworn as you have done this. (lines 54-59)
All of these quotations demonstrate not only the depth of Lady Macbeth's ambition, but also how far she is willing to go to guarantee her husband's success: if he is able to reach their goal, they will both reap the rewards.