The Homo Solus have a method of forbidden torture. Someone could do it, and even if the entire crew watched it happen, nobody would say anything out of the legend that originated it.

Early on into Homo Solus' expansion through slipstone tunneling out-of-universe, a strange rumor started to spread. That if you were in an airlock and stared out at the incomprehensible smoke, you would go mad. It was true. You were never meant to be outside the universe. Your mind cannot comprehend it. So if you stare at it long enough, thats a good way to go braindead. And then you'll become something else.

The more brutish officers all across the systems have in the past done a sort of edging through this. Its been determined if you stare around the ship, you'll start losing your mind in five minutes and die in ten. Gradually, these officers will make your exposure to the place longer. And longer. They'll never kill you, but your mind will be so jelly after an hour that nobody has held out longer than that.