The theme of duality is central throughout Hell Bent and manifests in the interplay between the human and the supernatural. The demons are dark reflections of the characters they pursue. They represent each individual’s duality, highlighting their darkest fears, regrets, and unresolved conflicts. The implication in the novel is that one side will eventually win, consuming the other.

The demons mainly appear as individuals who had a negative impact in the past on the person they are hunting. This connection ties the characters’ past actions and choices to present negative consequences. The majority are people they killed, but for Galaxy Stern, it is Hellie. Alex does not regret the people she killed, but Hellie becomes a specter of her guilt and remorse because she is an innocent bystander, reminding her of the consequences of her choices and her inability to save innocents from becoming collateral damage. These demons take on aspects of the characters themselves, mirroring their inner conflicts and vulnerabilities:

Alex took in the warm hue of Blake Keely’s hair, something like the bright red of Dawes’s bun. Detective Carmichael had been wearing a cheap suit when she’d first glimpsed him, but now that suit looked sharp, […] something Turner might wear.