The supernatural in A Midsummer Night's Dream is mostly represented by the fairies. In addition, the most dominant theme in the play is illusions. More specifically, most of the Athenian characters have their own illusions and while in the woods they become disillusioned, but their illusions are also restored. It is due to the fairies' conduct that the Athenians become disillusioned, but the fairies also restore their illusions. Hence, one role of the supernatural in the play is to point out that the nature of mankind is to be guided by illusions as well as to nurture those illusions.
While even the mechanicals have their own important illusions, all four of the Athenian lovers are also proven to be guided by illusions. Hermia and Lysander run from Athens into the woods because they are under the illusion they are in love and need to escape Athenian law condemning Hermia to death if she does not marry Demetrius. Demetrius even pursues her into the woods because he is under the illusion he is in love with her. However, all love is proven to be merely an illusion when Puck mixes up the lovers and uses a magical flower to make both Lysander and Demetrius now in love with Helena. Since both men switch so easily from loving Hermia to loving Helena, we can easily see that Shakespeare is portraying their love as being just an illusion. Essentially, through his mix-up, Puck has made the lovers become disillusioned about love. Mankind's ability to become both so easily guided by illusions and disillusioned is part of what makes mankind so foolish, which is best portrayed in Puck's famous lines, "Shall we their fond pageant see? / Lord, what fools these mortals be!" (III.ii.115-16).
However, the couples do not remain disillusioned. Instead, Puck, upon Oberon's command, rights his wrongs and pairs Demetrius back with Helena, whom he was engaged to before he started pursuing Hermia, and Lysander back with Hermia, showing us that the role of the supernatural in the play is not just to expose mankind's absurdities but also to nourish mankind's illusions.