Sworn brotherhood

Blood brother can refer to one of two things: a male related by birth, or two or more men not related by birth who have sworn loyalty to each other. This is in modern times usually done in a ceremony, known as a blood oath, where having each person make a small cut, usually on a finger, hand or the forearm, and then the two cuts are pressed together and bound, the idea being that each person's blood now flows in the other participant's veins. The act may carry a risk due to blood-borne diseases. In modern times, some gangs have also been rumored to make blood pacts. The process usually provides a participant with a heightened symbolic sense of attachment with another participant.

Örvar-Oddr's saga contains a notable account of blood brotherhood. The Norwegian warrior Örvar-Oddr felt a desire to test his fighting skills with the renowned Swedish warrior Hjalmar. Thus Örvar-Oddr sailed to Sweden with five ships and met Hjalmar, who had fifteen ships. Hjalmar could not accept such an uneven balance of strength and sent away ten of his own ships so that the forces would be even. The two warriors fought for two days with a lot of blood-letting and poetry, but it was a draw. Finally, they realized that they were equals and decided to become sworn brothers by letting their blood flow under a strand of turf raised by a spear. Then, the strand of turf was put back during oaths and incantations.

In the mythology of northern Europe, Gunther and Högni became the blood brothers of Sigurd when he married their sister Gudrun; in Wagner's Ring Cycle, the same occurs between Gunther and Wagner's version of Sigurd, Siegfried, which is marked by the "Blood Brotherhood Leitmotiv". Additionally, it is briefly stated in Lokasenna that Odin and Loki were once blood brothers.

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