Agave was one of the fifty Danaids (Daughters of Danaus) who took part in the mass marriage to the sons of Aigyptos. Agave married Imbros (whose mother was Argyphia). That night Agave along with forty-eight of her forty-nine sisters slew their husbands.
When Agave and the other Danaids who had murdered their husbands they were sent to Tartarus and were forced to carry water from the river Styx in bowls (or jars according to some) with holes over to a tub which leaks at multiple parts. Agave and the others were told only when they filled the tub could they wash away their sins. The Danaids continue this essentially impossible task to this very day.
Danaus & Europe
"...of the rest Busiris, Enceladus, Lycus, and Daiphron obtained by lot the daughters that had been borne to Danaus by Europe, to wit, Automate, Amymone, Agave, and Scaea."