The Abduction of Persephone

Classic short myth:
Hades, god of the Underworld, seeks out a wife to make his queen and eyes Persephone, Demeter's daughter. When he approached Zeus about it, Zeus did not oppose their marriage, but he did warn that Demeter would never consent to having her daughter live in the underworld. Hades then resolved to abduct her, appearing in a chariot one day while Persephone was out in the fields. He whisked her off to the underworld, leaving Demeter in an absolute rage. Demeter brought ruin upon plantlife and livestock on the surface, demanding that Hades return Persephone at once.
Zeus only intervened when he realized that if Demeter were to continue, mankind would die on the Earth, and no one would remain to make sacrifices to the gods. He sent down Hermes to collect Persephone from Hades, but Hades had already played his trick; Persephone had starved herself from the moment she arrived in the underworld, and Hades offered her pomegranate seeds to appease that hunger before she left, of which she had six seeds. Because she consumed food from the underworld, she was condemned to stay there for one month of the year per seed.
Rhea, mother to Demeter, Zeus, and Hades, proposed a deal: Persephone was to remain in the underworld with Zeus for half a year and return to Demeter for the other half, which Demeter reluctantly accepted. Back in the underworld, Persephone became feared by many, and kept Hades in check.