This is from a novel I read sometime in the 1970s or 1980s.
In the middle of the novel there is an expensive artist, who caters to the rich. He can telepathically see images inside the minds of his clients. For a hefty fee he can take a special sphere filled with colored specks, telekinetically move the specks to make a three-dee representation of the image haunting his client, then hit the button to freeze the specks to make a permanent image.
In the story, the current client is a young boy who has a nightmare of some ghastly squid or octopus-like creature. The boy's wealthy father sends him to the artist to make a sphere image of the monster, to help the boy get over his nightmare. The boy is quite pleased with the representation, says it looks just like his nightmare.
As it turns out the artist is also a secret agent for another interstellar empire. He needs to send a message to the foreign empire he is pretending to be a citizen of.
So the artist makes a second sphere containing the squid monster, superimposed on top of a star map of the foreign interstellar empire. He secretly sends it to the local government representative along with a threatening note.