This is like an Eldritch encounter for the fish.

Ripped out of his own environment, shown things way beyond its comprehension, before being tossed back to your plane to cope with what you have witnessed

Yeah, this is what a lot of people don’t initially understand about eldritch horror. The horror isn’t in seeing something scary. The horror is that seeing that thing teaches you things that you can’t even comprehend.

Imagine if there was a living, breathing, real two dimensional creature. It’s a stick figure on a piece of paper. All it knows is is up, down, left, and right. As far as it is concerned, the infinite X/Y plane is the entire universe. And then one day, you rip it off of that sheet of paper and drop it into our 3D world. And it can’t even begin to comprehend what it is experiencing. It literally doesn’t have the right sensory organs to experience 3D life. It struggles to understand anything. And after letting it experience 3D life momentarily, you simply stick it right back onto the paper where it came from. The stick figure screams, for it knows the universe is much larger than any of their friends believe… But it doesn’t even have the right words to describe what that larger universe is, because it doesn’t even understand it in the first place.

That is where the mind-melting horror comes from. To an eldritch being, teaching us anything is like teaching calculus to an ant. Anything it tries to teach us is just going to be useless, because we won’t even have the ability to process the information after we’re dropped back into our current existence. Even if it’s not trying to teach us anything, the simple fact that we encountered it is enough for us to start seeing things we can’t even comprehend. But we’ll know it exists. We’ll know it’s out there somewhere.

Yea this is basically Lovecraft in a nutshell.