The following might be what you're looking for: GURPS Zombies: Day one https://www.sjgames.com/gurps/books/dayone/ World of horror https://www.sjgames.com/gurps/books/worldsofhorror/
GURPS Celtic Myth, GURPS Arabian Nights, and GURPS Mars
The following might be what you're looking for: GURPS Zombies: Day one https://www.sjgames.com/gurps/books/dayone/ World of horror https://www.sjgames.com/gurps/books/worldsofhorror/
GURPS Celtic Myth, GURPS Arabian Nights, and GURPS Mars