Agave was the daughter of Cadmus, the King of Thebes and a sister of Semele, the mother of Dionysus.
Agave used to be jealous of her sister Semele because Zeus, the king of the gods, fell in love with her and their union created Dionysus, the Greek god of wine. So she spread the tale that Semele had actually laid with a mortal and then falsely put the blame on Zeus, and that Zeus, disgraced by the blasphemy, eventually punished Semele by striking her down with his thunderbolt.
When he grew up, Dionysus decided to impose a heavy punishment on Agave who shamelessly dared to question his divine origin. So he decided to return to the city of Thebes, where he was born and the grave of his mother lied. During that time, Pentheus, the son of Agave was reigning.
Once there, Dionysus ordered all the women of the city to go to the mountains and get intoxicated in order to praise him as a god of wine. However, Pentheus didn't agree with the cult. Wanting to put an end to it, he secretly followed the worshippers to spy on them. When his drunk mother Agave saw him, she took him for a wild beast. In her frenzy, she tore him to pieces and devoured him.