This kind of imagery shouldn't shock you, Shmoopers. The poem itself is a prayer… though it is anything but typical. Demeter is mad, see, and she's not so much praying to Hades as she is… threatening him. Faith in anyone, she says in line 4, comes at a cost. They may betray you the way that Hades betrayed her. So when she commands, in lines 14-15, that he go ahead and "believe in [him]self," she isn't exactly giving him some feel-good advice. She wants him to suffer the way those that have faith in him do. Don't those in power often forget to look after the little people? At the same time, don't we, too?