Zeus, king of the gods, is very hands-off when it comes to the whole situation with Core, Demeter, and Hades. In fact, he makes an appeal to a higher power in order for any movement to be made. He realizes that he will be unable to get either Demeter or Hades to budge. A mother will not be without her daughter, and Hades is smitten with love.
So with two forces that refuse to move and make headway, Zeus takes the only rational course of action. He tells on them.
Yep, he went to his mom, Rhea, to force his two siblings into action. It doesn’t matter that Zeus is king of the gods, this essentially boils down to a family squabble, and neither Hades nor Demeter are going to listen to their little brother, no matter how powerful he is.
Rhea behaves very much like a mother and works out a deal. If Core had not eaten the pomegranate seeds, then she would simply have been returned to Demeter, but because of the seeds, she belongs to the underworld. So they split the difference. Depending on the myth it’s either 3 or 6 months, but Core must spend part of the year in the underworld, and she is to marry Hades.
This myth has often served to explain the progression of the seasons. During spring and summer, Demeter gets to spend time with her daughter, and is happy. During fall and winter, Core leaves and so Demeter is sad, the seasons reflecting her mood.
But we’re not done yet. This myth has vast significance packed away in its few pages.