Chapel Perilous is a stage in the magickal quest in which your maps turn out to be totally inadequate for the territory and you’re completely lost. And at that point you get an ally who helps you find your way back to something you can understand. And then after that for the rest of your life you’ve got this question: Was that ally a supernatural helper, or was it just part of my own mind trying to save me from going totally bonkers with this stuff? And the people I know who’ve had that kind of experience, very few of them have come to an absolutely certain conclusion about this.