The Engineers, Pilots, Space Jockeys, Mala'kak, or Ossians are the main antagonists of the Science Fiction film Prometheus.
The Engineers come from an unknown homeworld. Their technology is very advanced, but it's especially advanced in Genetic Engineering. The Engineers are credited for the creation of humanity, and are revered as gods for their part in their origin. However, they later decided that humanity needed to be exterminated for reasons unknown. However, it seemed like a civil war took place on the their world, and it nearly wiped all of the Engineers off the face of the planet, leaving one in a dormant state.
Many people believe in the Space Jesus theory. In the theory, the Engineers sent a genetically engineered human/alien-hybrid to Earth to teach humanity tolerance and hospitality. However, humanity ends up executing Jesus on the cross, and the Engineers were disgusted by this senseless brutality. They then built weapons of mass destruction so that they could destroy the human race after their project failed.
Some people also believe that a civil war was enacted on the Engineers' homeworld, and it was waged between those Engineers who thought that humanity was a terrible idea, and those that saw them as beneficial. This could explain the one Engineer that seemed to escape his species' extinction.