From Lost Fables Wiki
Demi-Celestial blood, by and large, is a light red or pink color, and is slightly lighter than the blood of a mortal. Though it has a coppery scent, it also has undertones of fresh rain. Demi-Celestial blood does not stain clothing, coming out with a simple wash, and it slowly evaporates at room temperature. If heated up while not under pressure or contained, it rapidly dissipates.
Gathering Demi-Celestial blood is a matter of getting one of the beings to "allow" you to draw blood. They can safely lose up to two liters per age, but no more than 500mL in a day. A single dose is one liter.
The standard use of a Demi-Celestial's blood is coating one's blade in it before fighting a demon, as their blood is extremely poisonous to the fel beings. Beyond this, all sorts of anti-demonic alchemical items can be created using the blood of a Demi-Celestial, from potions which specifically defend against demons, to making poisons which only effect them. Recently, the Rehk-Ug have discovered that drinking a shot, about 30mL, of the blood of a Demi-Celestial, brings a blissful high like no other, making the user's body go limp for about an hour while they have an ecstatically euphoric out of body experience. Demi-Celestial blood abused in this way is extremely addictive. If you use it like this, roll a 1d100. If you get below a 65, you become addicted, requiring a shot each OOC day, or your character begins having seizures and losing the ability to keep food or water down. Your character becomes weaker and weaker over the following OOC days unless you feed your addiction, requiring a 1d100 roll once each day you do not. You must get 2 rolls in a row above 50 to kick your addiction. If you ever roll below 5 on the fourth day or any day thereafter, your character perishes of heart failure during a seizure.