Promethium is a chemical element that spells 'disappointment' on the periodic table. It is named after Ridley Scott's film Prometheus (movie) which was supposed to blow us all away but came out as a dull thud.
Trace sources of Promethium can be found in the Alien Crystals (and their sequels). When mixed with Expectation and Hype, Promethium makes a lot of noise but is all flash and no bang when delivering entertainment. Unstable isotopes and incomprehensible plotting make anyone having direct contact with Promethium bilous for a week.
Promethium is named after Prometheus, a rebellious Titan who stole Zeus's cookbook and matches from Mount Olympus and gave them to Man to start shows like Masterchef. Zeus was so upset that he had Prometheus chained to rock and let him be feasted upon by a liver-hungry eagle every day. This painful torture was then used to described the experience of audiences staggered from a screening of Prometheus in shocked disbelief at what they had just seen.
The commercial uses of Promethium are to raise money for a next film or for a television adaptation to an existing proposal. Ridley Scott has been particularly adept at finding a lot of Promethium in film franchises. Who remembers the amount of fanfare for the delayed sequel to Blade Runner? By the time it was released, Harrison Ford was too old and a computer-generated Sean Young hadn't aged a day since 1980. Ford had (which incidentally proved that he had never been a Replicant).
The biggest source of Promethium was found in a film backlot in Hollywood. Geologists say there is enough raw Promethium to finance more disappointing movies.