These extraterrestrials lived on a very distant planet called Nibiru, a planet that enters our Solar System once every 3,600 years.
Many descriptions and stories tell how Nibiru is much bigger than our planet Earth, and fully abundant with iron oxide, making its oceans and rivers red.
Sumerian tablets and inscriptions tell how the atmosphere of Nibiru started to deteriorate and become a hostile and dangerous environment.
Anunnaki needed an important element in order to continue to live on their planet: gold.