Blood

Blood is the name given to a liquid biological substance in organisms, like humans, that carries oxygen throughout the body. According to the Book of Shadows, warlocks do not bleed when wounded, implying they do not have blood in their bodies. The substance is drunk by vampires, who require it in order to survive, and it is also used in several spells and potions, either for blessing or as an actual ingredient.

The warlock Nicholas possessed the power to boil blood and kill his victims from the inside. When alchemists transmute an individual's blood, previous spells or potions based on that blood will be rendered ineffective, as was the case with the Belthazor vanquishing potion.

In Witches
In witches, their powers appear to be in their blood, which explains how powers are passed down, so, should a mortal infuse their blood with the blood of a witch, they gain their powers.

In Innocents
The blood of the innocents was used as an ingredient to revive the Source of All Evil.

In Demons
Upper-Level demons have red blood, while Lower-Level demons like Scavenger Demons bleed green. However, the Source of All Evil bleeds black. When a Demonic Alchemist transmutes the blood of a demon, it renders all potions and spells derived from demon's original blood useless.

In Warlocks
Warlocks, or, at least, some warlocks do not bleed when wounded or their body is pierced, implying they have no need for blood.

In Gypsies
The blood of a gypsy is used as an ingredient in several potions, including the vanquishing potion used by Pilar, Phoenix and Patra on the Slave King and the To Separate a Witch from Her Powers potion.

In Vampires
Vampires require blood to survive, and use their long, sharp fangs to draw it from the veins and arteries of human beings. Should vampires drink blood while in bat form, it converts the victim to become one of their own.

Spells and Potions

 * In the To Call a Lost Witch ritual, blood is the final ingredient, and is spilled into a cauldron along with other ingredients before a chant is said.
 * In the Spider demon vanquishing potion, the original Charmed Ones used their blood to bless the vanquishing potion they mixed to kill the Spider demon.
 * In The Slave King vanquishing potion, which was used by Pilar, Phoenix and Patra to vanquish the Slave King, Gypsy blood was mixed with Henbane and Mandrake Root as an ingredient.
 * The blood of the Twice-Blessed Children is considered to be one of the most powerful ingredients and forms of blood, as it contains many magical properties.
 * The blood of any related magical trio is significantly stronger then the blood of a single mortal and even magical person.
 * Different demons bleed in different colors, while some demonic beings do not bleed at all, implying that they do not have blood in their body.

Scrying
Blood can also be used by witches and warlocks in the art of scrying. The blood of the demon or person sought is applied to the scrying crystal, which is then swung over a map.