At Delphi the Theophania (Θεοφάνια) was an annual festival in spring celebrating the return of Apollo from his winter quarters in Hyperborea. The culmination of the festival was a display of an image of the gods, usually hidden in the sanctuary, to worshippers. Later Roman mystery religions often included similar brief displays of images to excited worshippers.
The appearance of Zeus to Semele is more than a mortal can stand and she is burned to death by the flames of his power. However, most Greek theophanies were less deadly. Unusual for Greek mythology is the story of Prometheus, not an Olympian but a Titan, who brought knowledge of fire to humanity. There are no descriptions of the humans involved in this theophany, but Prometheus was severely punished by Zeus. Divine or heroic epiphanies were sometimes experienced in historical times, either in dreams or as a waking vision, and frequently led to the foundation of a cult, or at least an act of worship and the dedication of a commemorative offering.