Unbricking a kiln after a firing is like uncovering buried treasure.

"Uncovering buried treasure" maintains parallel structure with "unbricking a kiln".

Leading with "a person" was unnecessary, too.

In a few days, when the kiln has cooled, Ellen opens the chamber, revealing the results of her labor and of the fire’s magic.

"of her labor" and "of the fire's magic" maintain parallel struture.

Others, salt-encrusted, “sleep” in ancient caverns, waking after centuries to feed and to breed.

"To breed" maintains parallel structure with "to feed".