Hecate is an ancient Goddess who is presented mostly as a triple formed Goddess: triple headed, triple bodied, six armed and six legged. I also found that "earliest Greek depictions of Hecate are single-faced, not three formed" (wiki), and that her mystic nature was created later.
|Ancient Hecate, 3rd century BCE|
In the Michael Strmiska's book "Modern paganism in world cultures" I found the lines about the origin of witchcraft and Hecate's cult, where the author says that Hecate conflated with Diana (Roman Goddess) was a protector of witches and sorcerers in their work and was most active at night. This then, in late antiquity and early medieval period, gave a ground for association of Hecate with witchcraft and night rituals.
According to Greek tradition Hecate can be called the first Goddess in humans history which used to have links with witchcraft and officially could be called as a Goddess of witches. However, in my opinion, we can't really know how she was treated by ancient Greeks and did they really worship this side of her deity. For that matter I also would like to know about the magic as a tool of mortal people in ancient Greece. How they used magic and how magic was treated that time.