What happens in the NH4Cr2O7 with HgSCN reaction?
I can't comment on the metaphysical aspects ;)

This experiment is known as Pharaoh's snakes, and it is indeed impressive.

Upon heating, mercury thiocyanate decomposes to yield mercury vapour, carbon sulfide, and dicyan (ethanedinitrile):

$$\ce{2Hg(SCN)2 -&gt;[\Delta] 2 Hg + 2CS2 + (CN)2}$$

As a result, the solid starting turns to a foam-like mass. 

The effect is amplified due to the presence of ammonium dichromate, which oxidizes the carbon disulfide to sulfur dioxide and carbon dioxide.

The experimenter is apperently aware that quite a lot of rather harmful components are released and therefore has decided to run the show in the fumehood and closes the window immediately after igniting the mixture.