The featureless mirror mask of the Alchemist became my new alien, perhaps something such as the alien King that people always talked about or the Primogenitor that they also talked about. I imagined that the mask became a gelatinous covering which could shape shift and a maw would open up through which the alien's inner mouth and skull would be at times visible. I thought that the original Alien's face could not be beaten so it was time to withdraw from anything further interesting and new.
It looked though in Prometheus concept designs, they were asking the same sorts of questions looking at the same sort of concept and my thoughts about an alien inspired by the alchemist and an alien layer inspired by his seemed even more important
See: Vidocq at the Alien Explorations site