Vampire Hunters

I personally would only suggest chasing hunters either early on before you have many powers, or on your Perception quest.
Hunters can be a great source of coins, but can hurt
your blood count as well.

What are Vampire Hunters?

A new element comes to the city - food that fights back.

Vampire Hunters look just like normal humans, though it has been suggested
that if you sit in a square and refresh the screen you may see a human that
appears to move around (remember the 120 hit limit if you haven't donated
though). On entering a square with a hunter you will get a message like:

"There's a vampire hunter! He shoots you with a crossbow bolt for 50 damage,
and runs to the northeast."

* The hunter may be either male or female.

* The hunter may cause as little as 10 blood damage, but it seems that the
maximum is 50.

* The hunter can run in any direction.

If you follow the hunter (in this case into the square above and to the
right of your position), s/he will attack you and move on again. If you
have enough movement points to keep chasing you will eventually see the
hunter turn green and s/he will not move on after attacking you. At this
point you can drink the hunter and you will hopefully be rewarded with
a larger than normal amount of both coin and blood.
If you have perception, all hunters will appear in “green”.

As far as we know Hunters are not harmed or affected by Scrolls of
Turning, Holy Water, etc.

Well, It wouldn't really make sense for -vampire hunters- to get hurt by holy water