The war hero becomes a murderer and then dies a shameful and violent death. Shakespeare creates an atmosphere of evil and darkness mainly through his language, although scenes containing violent actions or the witches are often played in darkness. The language gives an insight into the character of Macbeth - we see his ruthlessness and cruelty, but also fear, doubt and some scruples. Macbeth is connected with the supernatural in the audience's mind from the onset. This is the first thing that is not consistent with Macbeth's image of a war hero.
Asides are very important because they give the audience an insight into the character's mind.
Once the audience knows how the character thinks, they tend to sympathise with him, which is another reason why 'Macbeth' is a tragedy. The aside follows closely Macbeth's desires and doubts - he does not know whether 'this supernatural soliciting' is good or bad, but he dearly wants to be king. Macbeth is drawn to darkness, because he believes that it will hide his evil deeds. Macbeth is afraid that people will realise that he wants to be king and is prepared to kill for it, so he calls on the stars to hide their light, so people cannot see what he is thinking. This is again in an aside, so the audience are the only ones who know what Macbeth is thinking.