Jim Marrs has written about it.  The Nazi’s derived their technology from them. They have left, but according to Russian leaks, they are back. Who are they? Interdimensional beings who want to reclaim what is theirs.  Putin knows and has threatened the US with full ET disclosure. Here is the story complete with the background, the ancient history and the connections to the Nazis.  Soon, I will be revealing much more and the source is an ex-NSA agent. .