Puck is loyal to Oberon and will do anything the fairy king asks of him. At the moment the king and h is queen, Titania, are in a dispute over an Indian child whom she has adopted. He wants to raise the child in his ways but Titania won't give him up to him.
Oberon gives Puck the assignment of enchanting Demetrius, however, Puck muddles things up.When Oberon sees that Puck has mistaken Lysander for Demetrius so that now Lysander is in love with Helena when he should be in love with Hermia, Oberon tells Puck to fly “swifter than the wind” and to use “some illusion” to bring Helena to there part of the forest where Demetrius is at (III.ii.95,99).