Most will tell you your blurb is too long. The sweet spot is supposed to be 100-150 words. I'm not totally sold on that, and there have been good arguments that a blurb should be as long as it needs to be, but I do feel yours could be substantially tightened and wind up with even greater impact.
Also, big blocks of text are supposed to make agent's eyes glaze over, so you should consider breaking it up (logically, of course).
You say "As Isla slowly regains fragments of her memories", is that supposed to be Analise?
Overall, I feel you have the raw material for the blurb, but as written it doesn't resonate with me. You have passive voice (e.g., "When it is revealed") which I feel weakens the blurb. I also feel you have too many descriptors. Most people will get that Hell is a bad place that needs to be kept out of the world, so "wicked souls from the deepest nadirs" feels overdone to me.
Also, big blocks of text are supposed to make agent's eyes glaze over, so you should consider breaking it up (logically, of course).
You say "As Isla slowly regains fragments of her memories", is that supposed to be Analise?
Overall, I feel you have the raw material for the blurb, but as written it doesn't resonate with me. You have passive voice (e.g., "When it is revealed") which I feel weakens the blurb. I also feel you have too many descriptors. Most people will get that Hell is a bad place that needs to be kept out of the world, so "wicked souls from the deepest nadirs" feels overdone to me.
Hopefully this helps somewhat.
Good luck!