From Lost Fables Wiki
Withered blood is 260 degrees Fahrenheit, boiling hot and never cooling, unless it hits dirt or sand, or some cloth it can absorb into. If it does, it rapidly cools, but if it is kept in a water skin or glass bottle, it will forever remain burning hot, making it a fairly useful item, even if it had no alchemical uses.
Withered are very likely to recognize the utility of using their own blood, and thus are significantly more likely than any of their cousins to give up their blood for all sorts of reasons. They can safely lose up to two liters per age, but no more than 500mL in a day. A single dose is 1L.
Withered blood can be used very effectively as a weapon, as a flask of boiling, sticky blood to the face is a devastating attack. It can also be used in a plethora of summoning rituals for demons, and is almost certain to get a result. Besides these uses, when used as an alchemical reagent, withered blood temporarily increases the magical power of the person using the alchemical mixture, making any Truth they use about 50% stronger for the following 6 rounds. This increase in power uses the magical energy in the blood, rather than the Truthseeker's own soul. When made into a paint, it increases the power of enchantments by 50%. This cannot be mixed with other ingredients.