Eater barriers only ever really defend against a few types of collision. That's just a function of how eaters work - they only ever eat a small subset of things that can be projected at them.
I don't think anyone has ever created an impermeable wall in the GOL. I am pretty sure that such a thing is impossible - though AFAIK, that has never been proved.
Conway’s Game of Life is Turing-complete. Therefore, it is possible to create an AI in it. If you created a 3^^3 by 3^^3 Life board, setting the initial state at random, presumably somewhere an AI would be created. Would this AI somehow take over the whole game board, if given enough time?
Would this be visible from the top, as it were?
EDIT: I probably meant 3^^^3, sorry. Also, by generating at random, I meant 50% chance on. But any other chance would work too, I suspect.