Before the word alien has been generalized in a connotation similar to monster, Tarkovsky already had an alluring interpretation of this creature.
In Solaris space station, the alien is actually a requiem to repressed memories of each person, it comes alive and perfectly resembles someone from the past. This creature has formed as consequential matrixes of the radiation experiment that projected through the planet's ocean.
As the common mythical allegory of alien, it's never real enough to the people on…