Bromius is another name for Dionysus, the son of Semele and Zeus. Zeus' jealous wife Hera discovered the affair and contrived to influence Semele to request that Zeus revealed his true form to her. Once Zeus has promised his lover that he will grant her any wish, she asks to see him in his godly appearance (an event referred to in antiquity as an epiphany).
Dionysus is also known as Bromius, the offspring of Semele and Zeus. Hera, jealous of their relationship, concocted a scheme to persuade Semele to request that Zeus reveal his true divine form (a phenomenon referred to in ancient times as an epiphany).