The appearance of the ghost helps create an eerie mood and grabs the audience's attention. The ghost does not speak, which adds mystery and suspense. An audience would probably want to know more about why the ghost is there and what it will do. Should be right :)
The ghost adds an element of suspense and mystery to the whole plot. The readers will be more interested in the story and will definitely be on alert to know what how the story will turn. Also, it gave an eerie feeling to the whole setting of the story, fixing the attention of the readers and audiences into the plot and story.
Explanation:
The ghost first appeared to Bernardo and Marcellus, the two watchmen on guard duty. When the scene opens, we see them joined by Horatio, a friend of Prince Hamlet. They told him about the appearance of a ghost who looked like the previous king. And he again appeared to them twice that same night, though not uttering a word or sound. This appearance of the ghost provides a mystery and suspenseful nature of the play. It also gives an eerie feeling to the whole scene, with the audience/readers eager to learn more about it. The readers would want to now more about it and will definitely be fixing their attention to the ghost in particular. Moreover, the likeness of the ghost to the now dead former king will immediately pique the interest of the audience, knowing there must be some plot going on that is in itself important. The involvement of the dead king will likely provide some unexpected twist to the whole play, thus making the audience eager to know more.
