There has been much talk about a Planet Nibiru, often referred to as Planet X, or a hidden planet in our solar system. First reference of Nibiru comes from Sumerian texts saying supposedly every 3600 years this planet enters our system and was inhabited by the people called Anunnaki. Some refer to them as the Nephilim (referred to in the bible) and the belief was that it was the planet gods came from.
It was said they came to earth and were very powerful, controlling, and with unending appetites. This is very much in alignment with Native legends around the world of a race of cannibalistic giants. It was also said they came here for gold and mining it. Their planet supposedly was devastated and they scattered all through the stars finding new homes.
Recently, scientists detected a planet 2 to 4 times bigger than Earth which would make it the fifth largest planet. It is believed to be behind Pluto in an icy dark region. Gravitational effects have led them to believe it exists.
For now, they are referring to it as Planet 9. I am reminded of a horrible Ed Wood movie, "Plan 9 From Outer Space."