The bottle of blood is an item used in The Branches of Darkmeyer. It is given to the player by Valentina Kaust, who states it's fine quality blood given to her by a friend that smuggled it in from Canifis. According to her friend, this blood is from their special stock reserved for Vanstrom Klause.
Before drinking the bottle there will be a warning stating it will have harmful effects. If the player choose to drink the blood, they will take damage equal to half of their life points. If the player chooses not to drink it the player smash the bottle on the floor and will have to explain to Valentina why they did so.
Doing this task offers a lot of status and can easily turn a Vyreling into a Vyre Grunt even if all the middle tier tasks are not done.