Goddess of the harvest, grains and fertility of the earth. She presided over the cycle of life and death.
In some versions of the myth, she got real mad when Persephone was nowhere to be found (in that time she was exploring the underworld) and basically threw the worlds largest shit-fit. She made all the crops die and the world barren until Zeus actually did something good for once, found Persephone, and decreed that she would spend half the year with Hades and half the year with her mother. For centuries after, winter would be caused by Demeter’s depression for the months that Persephone was off leading the Underworld.