Shelley uses personification in that last stanza. The Cloud is the child of both the Earth and Water. Then as the rain clears, the Cloud once again is reborn. But Shelley again uses the human experience of childbirth when he uses the words "Like a child from a womb." This human connection appeals to the emotional senses in the reader. He also gives the oceans and shores "pores," as if they, too, are human.
"I am the daughter of Earth and Water,
And the nursling of the Sky;
I pass through the pores, of the ocean and shores;
I change, but I cannot die --
For after the rain, when with never a stain
The pavilion of Heaven is bare,
And the winds and sunbeams, with their convex gleams,
Build up the blue dome of Air --
I silently laugh at my own cenotaph
And out of the caverns of rain,
Like a child from the womb, live a ghost from the tomb,
I arise, and unbuild it again."
Another sense that he plays with is sight. He gives the rain purity when it cannot stain the "pavilion of Heaven."
All the while Shelley is just describing the cycle of a typical cloud any day of the week.