A blood ritual is any ritual

Ritual

A ritual is a set of actions, performed mainly for their symbolic value. It may be prescribed by a religion or by the traditions of a community. The term usually excludes actions which are arbitrarily chosen by the performers....

 that involves the intentional release of blood.

A common blood ritual is the blood brother

Blood brother

Blood brother can refer to one of two things: two males related by birth, or two or more men not related by birth who have sworn loyalty to each other. This is usually done in a ceremony, known as a blood oath, where the blood of each man is mingled together...

 ritual, which started in ancient Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 and Asia

Asia

Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

. Two or more people, typically male, intermingle their blood in some way. This symbolically brings the participants together into one family. This can be an unsafe practice where blood-borne pathogen

Pathogen

A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

s are concerned; the use of safe, sterilized equipment such as a lancet

Scalpel

A scalpel, or lancet, is a small and extremely sharp bladed instrument used for surgery, anatomical dissection, and various arts and crafts . Scalpels may be single-use disposable or re-usable. Re-usable scalpels can have attached, resharpenable blades or, more commonly, non-attached, replaceable...

 can mitigate this problem.

Body piercing

Body piercing

Body piercing, a form of body modification, is the practice of puncturing or cutting a part of the human body, creating an opening in which jewelry may be worn. The word piercing can refer to the act or practice of body piercing, or to an opening in the body created by this act or practice...

 can also be part of a blood ritual. Though piercing does not always cause bleeding, it certainly can. Piercing has been practiced in a number of indigenous

Indigenous peoples

Indigenous peoples are ethnic groups that are defined as indigenous according to one of the various definitions of the term, there is no universally accepted definition but most of which carry connotations of being the "original inhabitants" of a territory....

 cultures throughout the world, usually as a symbolic rite of passage, a symbolic death and rebirth, an initiation

Initiation

Initiation is a rite of passage ceremony marking entrance or acceptance into a group or society. It could also be a formal admission to adulthood in a community or one of its formal components...

, or for reasons of magical protection.

Blood rituals often involve a symbolic death and rebirth, as literal bodily birth involves bleeding. Blood is typically seen as very powerful, and sometimes as unclean

Unclean

Unclean may refer to:* Unclean animals, those whose consumption or handling is labeled a taboo* Unclean food, in Jewish dietary custom* Unclean hands, a term in contract law* Unclean , from 1984* Unclean spirit, in Christianity...

. Blood sacrifice is sometimes considered by the practitioners of prayer

Prayer

Prayer is a form of religious practice that seeks to activate a volitional rapport to a deity through deliberate practice. Prayer may be either individual or communal and take place in public or in private. It may involve the use of words or song. When language is used, prayer may take the form of...

, ritual magic, and spell casting to intensify the power of such activities. The Native American Sun Dance

Sun Dance

The Sun Dance is a religious ceremony practiced by a number of Native American and First Nations peoples, primarily those of the Plains Nations. Each tribe has its own distinct practices and ceremonial protocols...

 is usually accompanied by blood sacrifice.

Some blood rituals involve two or more parties cutting themselves or each other followed by consumption of blood. The participants may regard the release or consumption of blood as producing energy useful as a sexual, healing, or mental stimulus. In other cases, blood is a primary component as the sacrifice, or material component for a spell.

Blood Ritual. Circumcision, Talmud Style http://www.come-and-hear.com/editor/br_4.html Follow this link, references included on page.
Certain video games with a more occult theme have used blood sacrifice (or, as it is known in some, blood magic) as a source of magical power. Such video games include Dominions II

Dominions II

Dominions II: The Ascension Wars is a 4X turn-based, computer strategy game. It was developed by Illwinter Game Design and published by Shrapnel Games. The game was released on November 14, 2003 in North America for Microsoft Windows, Mac OS X and Linux....

.

"The Blood Ritual" is also a ritual created by L. Ron Hubbard

L. Ron Hubbard

Lafayette Ronald Hubbard , better known as L. Ron Hubbard , was an American pulp fiction author and religious leader who founded the Church of Scientology...

that invokes the Egyptian goddess Hathor.