Necromancers

Necromancers are people you see in potion shops when you've been scrolled repeatedly, holywatered or garlicsprayed. They sense your pain (when you've been hit for more than 100 bloodpoints, that is) and approach you if you've not healed too much since the attack by yourself - in short, you should try to find a Necromancer as soon as vampirically possible after an attack, rather than trying to gain back your blood the hard way via biting vampires and humans.

Necromancers will heal you up to 100 bloodpoints less than your previous amount - so if you have 4 000 and were taken down to zero, you can buy back 3 900 bloodpoints from the Necromancer for the price of 97 500 coins. The rate is 25 coins per bloodpoint - half the price of getting your bloodpoints back at the pub (bloodwine granting 1 bp for 50 coins; blood granting 2 bp for 100 coins; both resulting in a rate of 50 coins per bp), and far less action point eroding. You need a single action point to buy back all the 3 900 (if you have the money for it on you) from a Necromancer. You would need 1 950 action points to buy it back from a pub (blood).