This depiction of Kali and Shiva references the human experience of death. Kali, who represents dissolution mates with Shiva, who represents creation. She drives him mad and he forgets who he is. For a time, Shiva is lost. Such is death.
The growth of grace is like the polishing of metals. There is first an opaque surface; by and by you see a spark darting out, then a strong light; till at length it sends back a perfect image of the sun that shines upon it.