What happens when you discharge a 4,500 Volt capacitor into a bucket of copper sulfate? Apparently you raise the spirit of Cthulhu. He just happened to come back to us in the form of a tentacled ball of plasma. Copper sulfate (CuSO4), is a copper atom, a sulfur atom, and four oxygen atoms. Plasma happens when either heat or electric potential difference gets so large that electrons are stripped away from their atoms and swim around with the atoms in a kind of soup. The atoms that rise up from the liquid are a mix of positively charged copper atoms and negatively charged groups of oxygen and hydrogen.
The decorative yellow swirl is the plasma turning colors as it reacts with the air. Either that, or the elder god isn't potty trained.
Via Physics Central.