Viola can easily be perceived to be the central character of Shakespeare's Twelfth Night. She sets the plot in motion, being the first character to start stirring up action in the play, becoming the indispensable link between characters and is connected to every single one. Eventually, she aids the resolution of all the impediments of the story. Viola is also the most intelligent character, the only one without any obvious faults, unlike most of the others, who make the play humorous in a satirical way.
Firstly, Viola sets the play "in motion". It is her arrival on the island of Illyria which starts the confusion and chaos on the mythical island. Her poignant plight of the inconveniences with identity and disguise become the central crisis of the play. She also provides some level of comic relief at points in the play, due to the dramatic irony of the play, when the audience already knows that she is a woman, whilst the other characters are under the impression that she is not.
Viola's plan to dress up as a man and work for the Duke Orsino develops the first obvious dilemma of the play, apart from the unanswered love of Orsino from Olivia.
Viola provides the link between Orsino and Olivia. She is romantically associated with both of them in a "love triangle", as she falls in love with Orsino, while Olivia falls in love with her while she is disguised as a man. As she is professionally connected with Orsino, being his "eunuch" and servant, she must run errands for her master, sending Olivia his love. She is the messenger between the two of them, as they are no longer on speaking terms - Olivia rejects the love of Orsino and claims to be in mourning for her...