This is another “new/old” category because most mythological quests had supernatural elements to them. It became “new” when the mystery genre started having more beings, especially vampires.
What is the appeal of supernatural mysteries? Why are vampires so damn popular?
Well, for starters, vampires don’t age, they are “forever young.” They are dark heroes: vampires are not only dangerous, the well-known vampire protagonist/love interest characters seem also be to be forever brooding. This taps into an old romantic tradition (think Heathcliff in in Emily Brontë’s novel Wuthering Heights).
The impact of these books has been simply phenomenal. They not only are popular as books, they have spawned popular movies and TV series.