Task 3: Until WWII, the most famous part of the Catherine Palace at Tsarskoye Selo near St. Petersburg was the so-called amber room. It was looted, lock stock and barrel, by the Nazis, and has since vanished from the face of the earth, with its fate a complete mystery to the present day. Let your imagination run wild: What do you think may have happened to it? (Kidnapped by aliens? Spirited away by dwarves and hidden in a secret cavern deep below the face of the earth? Sold, piece by piece, to finance … what? The Nazi war effort? The restoration of the Romanovs to the throne of Russia? Stalin’s pogroms? What else?) Don’t hold back, we’d love to know!
Okay, so I've read a lot of the Harmony books by Jayne Castle. They're set on another world called Harmony. It was colonized when a curtain opened near Earth allowing travel between it and unexplored worlds/universes. One day the curtain suddenly closed, cutting off the settlers on Harmony from Earth. A couple of hundred later, the residents of Harmony have adapted and Harmony has a pretty modern-day Earth type civilization. With one of the exceptions being that they use amber to power things, and as a focus for their paranormal abilities.
My theory is that someone who is up to no good figured out a way to reopen the curtain covertly as well as having mastered the ability to time travel. They returned to Earth, traveled back in time stole the already stolen amber panels and contents of the room hence their disappearance, and returned to Harmony with no one any wiser. They did this so that they could conduct their nefarious experiments without raising suspicions about how much amber they were using.