Very well done and brilliantly designed. Balance may be a bit dependent on narrative but there are far worse things, even in WotC materials. Leaning hard into the Warlock's relationship with their patron will bring the most out of this work.
Three words: edgy, horrifying, original. Unfortunatly those things are so much rare nowadays, but this work is an exception. If you want to play with something really bizzare, ugly and the same time beautiful I encourage you have this product.