Published September 30, 2025 by Tor Nightfire
The third installment in T. Kingfisher's Sworn Soldier series sends Alex Easton somewhere they emphatically do not want to go: America. More specifically, an abandoned coal mine in West Virginia with a unsavory reputation. When their old friend Dr. Denton calls in a favor to help locate his missing cousin, who was last seen heading into that very mine, well, a sworn soldier answers the call.
I've loved following Alex Easton through the crumbling Usher estate and the fog-draped forests of Gallacia, so naturally I was eager to see where Kingfisher would take them next. And I have to say, the setting of What Stalks the Deep is its strongest asset. The darkness is absolute, the walls press in from every direction, and the silence of the mine is almost intolerable. Imagine being underground with tons of rocks between you and the surface. Kingfisher leans into the claustrophobia beautifully, and we experience it alongside Easton.
Kingfisher has always excelled at writing characters who feel lived-in and real, and that hasn't changed. Alex's particular brand of practicality bumping up against the inexplicable never gets old, and watching them navigate the landscape of rural West Virginia with acerbic bewilderment is funny. Angus remains a steadfast, grounding presence, and there's something quietly satisfying about the way these three have settled into each other. If you've come to love these characters across the earlier books, revisiting them is still a joy, even if the horror is light.
Where What Stalks the Deep loses a little steam, unfortunately, is in the horror itself. The monster at the center of this story never quite reached the level of wrongness that Kingfisher achieved with her possessed hares in What Moves the Dead — that specific, skin-crawling sensation of something familiar twisted just slightly out of true. Once the monster is revealed, it's almost...cute?
What Stalks the Deep is by no means a bad book. Kingfisher is too skilled a writer for that, and I'll pick up whatever Alex Easton adventure comes next without hesitation. But for me, the Sworn Soldier series has yet to top What Moves The Dead.