ok I'm looking for another one. A race from another plane/dimension kill off most of mankind and hunt the rest. A boy sees his father killed and iirc kills his dads killer and inherits his abilities, then starts hunting the hunters.
Ends up enslaving a female of the race, and sends a virus (flu) to the other dimension to kill them.
I've searched using the high fantasy and magic tags but didn't see it.
TIA,,,SS
