It's an extended meditation on death and the possibility of closure.

The Mind that went to the other side and came back, as a guest in another Mind, but had nothing useful to say about the experience, then after years abruptly disappeared. And the hosting Mind realizing their guest was really gone, purging any trace of the other Mind from their Mind. Maybe it would be a good power to erase people from my mind who are really gone.

When the guy who has plotting and scheming the entire book causing interstellar war, causing the destruction of a military base, and other shenanigans gets to the end, it's just him and a few others from his civilization having an awkward conversations that has nothing to do with all the mayhem he caused.

Maybe one of the morals of the story is any conversation with someone might be the last conversation you ever have with them.