From Lost Fables Wiki
Prodigal blood is thicker than that of their fellows, in addition to being a deep, vibrant purple. It runs slow, like molasses, and has a pungent, sweet tangy smell. It will not dilute into other liquids with the exception of alchemical bases, it will not boil nor freeze, and it will not absorb into cloth, though it will dissolve into dirt or sand.
One must draw the blood from an individual Prodigy, a difficult proposition indeed, as most of them will not believe that being bled for their magically potent blood will further their Purpose. If a Prodigy can be "convinced" to "donate" their blood, they can safely lose up to two liters per age, but no more than 500mL in a day. A single dose is a half liter.
Prodigal blood is useful for almost any conceivable alchemical or magical purpose. When used with a paint or paste, it can make those alchemical effects permanent, so long as the paint or paste remains. In the case of potions, it makes them far stronger, and last for longer. Beyond this, almost any creature interested in magic or blood would be incredibly interested in it, as prodigal blood is supposed to greatly increase the abilities of any voudr or demon which consumes it.