Make a hit on a Vampire listed to collect the bounty put on them. Or, if you've got a rival you need taken out, you can add that vampire to the list by tapping "Mark" on their profile page.
To put a bounty on someone, you need to carry enough blood required for that certain vampire. It is determined by calculating that vampire's blood flow per hour x 10.
e.g. : †96,080 every 60mins (54mins on Blood Thirsty vampires) x 10 = †960,800
You can't use your blood stored in blood bank to to mark someone.
Collecting bounties is an easy way of earning blood.
You don't need to win the attack to claim the bounty.
You just have to be the last vampire to attack and kill him.
Is there a benefit to someone putting a bounty on you? Yes. If your clan has the maximum amount of basic skills, protection, and undead curses for your level, then you are more likely to dominate the attacks.
Those successful defenses will add to your record of "Fights Won".