The key thing to know here is that there exists a model of spiritual enlightenment in which enlightenment is a horrifying and bleak thing. The adjective I’m going to use for this sort of enlightenment - Qlippothic - is important. Basically, it suggests that there is a form of enlightenment that can be found by encountering and contemplating the darkest parts of humanity. The Qlippoth refer to the hollowed out, vacant, and rotted shells of spiritual concepts. And the whole radical idea of Kenneth Grant is that there’s not actually a difference between those, which are basically the horrible nightmares within humanity, and actual enlightenment.
This is done really well in The Black Rainbow, and I’m glad to finally have a name for this!