Recs if you like Servant of the Underworld (Obsidian and Blood, #1)...

fantasy books that feature necromancy - with protagonists or antagonists as necromancers. for magic systems that are more than a little macabre

Books that either draw from elements of the Aztec civilizations (location, mythology, etc.)

List of fantasy, sci-fi and supernatural horror books and series where main character isn't involved in any romantic relationship during the course of the book or it is not prominent. No romantic subplots involving main point-of-view character(s).

Mystery novels set in rich, well-developed fantasy worlds. (This list does not include urban fantasy.)