Speaking from a GM's point of view, I consider this sourcebook one of the most interesting and helpful books I have read across many genres and game systems. Ι do not even think of it as a strictly MtA sourcebook. It has helped me understand and map out a group of evocative and terrible villains that have my players in thrall; and not even in a Mage game, but in a Pathfinder 2e one.

I love the fact it is not a crunch-book; it actually contains ideas that helped me depict evil believably. And I really appreciated the whole description of the Nephandic Descent; I hardly consider this player material. Unless, of course, the people who claim it is unnecessary for a GM, are all so well-versed and familiar with such concepts from the get-go. Because I wasn't, and I bought this book precisely for this reason.

As for the antisemitic characterisation: I hadn't bothered making this connection before reading about it in the negative reviews. Yes, I would have loved some different take other than the Kabbala, for variety's sake. Βut from reading a game sourcebook to making it a conspiracy theory, it is quite a long stretch.