Blood Rune

A blood rune, also known as a blood seal, is an alchemic technique used to bind someone's soul to an inanimate metal object. The iron in the blood will interact with the metal it is on, causing the object and the blood rune to form a symbiosis.

Al's Blood Rune/Seal
Al's Blood Rune/Seal is a Octogram

Octogram:Protection, spiritual enlightenment, resurrection, rebirth, infinity, and abundance. Balance between spirit and matter, the inner and outer bodies, and male and female. The octagram has been associated with the Star of the Magi, and is a symbol of hope and communication.

The Rune also may represent the "Quintessence" or "The Fifth Element"

The Quintessence is the fifth element with which the alchemists could work. It was the essential presence of something or someone, the living thing itself that animated or gave something its deepest characteristics. The Quintessence partakes of both the Above and the Below, the mental as well as the material. It can be thought of as the ethereal embodiment of the life force that we encounter in dreams and altered states of consciousness. It is the purest individual essence of something that we must unveil and understand in order to transform it.

The Process
The practitioner must draw a rune in blood on an inanimate object (usually armour) and then they give a part of their body to the gate and call the wanted soul into it, filling the object with the soul.

Positive effects
A person whose soul is bound to an inanimate object feels no pain, hunger or fatigue thus enabling them to perform immense physical feats. Also, as the person has no body, he or she can sustain more damage than normal humans, placing the person in a state of nigh invulnerability.

Negative effects
He or she has only one weak point, the rune itself. If the rune is in some way damaged, the persons soul will start to fade from the object. This makes the protection of the blood rune the most important task of the bound soul. Sometimes, the person inside the object will start to question his or her own existence. This can be very dangerous to the person's mental health. Yet there is a bigger danger. If one's soul is bound to an inanimate object for long, the soul and object will start to repel each other. The person will start to experience moments of sleepiness, which cause the person's soul to disappear from the object, as stated by Al in the manga. He says his body is like a time bomb.. This can lead to complete destruction of the soul as it slips away to The Gate. This makes the blood rune only a momentarily effective technique.

Examples

 * Alphonse Elric
 * Barry the ChopperBarry's_blood_rune.jpg
 * Number 48