While it took me a while to finally get around to the last book in the Demon Cycle series, I'm glad I put the time in to complete it. The initial concept laid out in The Warded Man was so interesting that I had to see it play out to the end. The Core wraps up this series with an ending that was mostly inevitable while also managing to add more subplots that merely padded out an already large conclusion to this series.
Overall, my main qualm with the Demon Cycle series is that it is a prime example of "Men Writing Women." This trope is evident in many places across this series but seems most egregious in The Core with its depiction of childbirth (especially the one at the beginning). I understand that many fantasy worlds are based on medieval Europe, but that doesn't mean the writer has to be so heavy-handed with sexism and misogyny. The fact that Leesha's character was written as a counterpoint to this doesn't hold up very well when she also eventually falls into these tropes.
Ultimately, The Core delivers on the "grand battle" between humans and demons that could only come about after the humans stopped killing themselves long enough to create an alliance against the demons. Even with a well-written climactic battle, it felt so delayed and crammed near the end of the book that it was almost a disappointment. However, the strength of the worldbuilding carried this book along, as it did in the previous books in this series. If you can ignore some of its rough edges, I recommend the Demon Cycle for anyone looking for dark adult fantasy.
An action-packed ending to a series with some "Men Writing Women" issues, I give The Core 4.0 stars out of 5.