You don't know that only if you didn't play EA and didn't pay any attention to information about Act 2, that was revealed lately. There are plenty of dark places in this game.
I haven't played early access and I haven't watched much of it, I deliberately avoided all that so I can experience the game fresh. I have watch the live stream by Larian and some areas looked darker but we don't know if it's like that by design or if those areas actually require dark vision.
