Macbeth 1.5 Language: "murdering ministers"

The transcript explores the concept of witches having contracts with the devil, assisted by evil spirits. It delves into beliefs about witches breastfeeding these spirits with a bitter liquid. The spirits are described as invisible unless they take animal forms. They are also depicted as waiting to cause natural disasters or exploit human weaknesses, such as Lady Macbeth's, to turn them into instruments of darkness.

What does 'nature's mischief' refer to in the context of the text?

In what way can Lady Macbeth be seen as an instrument of darkness?