They are just random characters. I wanted to make some dark and evil, but nevertheless eye-catching characters. :) Yes, their kingdom to be in the underground is a good idea.
"The Nightwalkers of the Blood Mountain"...? They could be brother/sister or just king/queen, whatever. Not vampires but adverse to sunlight and thus forced to go out only at night, hence called "nightwalkers". And their Blood Mountain could be an underground realm of blood-red rubies... :)
