Conversion Efficiency.

The demon lords and demon kings saw that the black aura had become tangible energy that was oozing and popping. Then it enlarged and swallowed the golden crown. 

They couldn't see anything anymore. They only felt the large fluctuations of spiritual power smashing against each other. The purple energy sea below was smashed by the shockwaves of these fluctuations. It became agitated as large waves formed on its peaceful surface. 

The first layer of the abyss was shaking as the two demon gods clashed. But no one could see what was going on anymore because of the black cloud. 

They didn't have to wait long for an outcome. A golden cloud was ejected out of the black cloud. It was vastly smaller than its previous size. It was also blotted with large black spots.