Seething is a literal translation of Seiðr, which is a type of sorcery which was practiced in Norse society during the Late Scandinavian Iron Age. Modern witches use seething as a way to shamanically get outside of themselves, into an altered state, and to raise the Power for charging a spell, tool, or talisman.
There are two modern interpretations of the practice of seething based on accounts in old Nordic sagas and other ancient literature. The first method is very much like the practice of Treading the Mill. The witch bears a gandreigh, or riding pole, such as a staff, broom, stang, hobby-horse, or wand. He then treads a wide circle while focusing power on a central point, such as a stang, altar, or lead witch. Alternately, the witch may choose to use their own gandreigh as the focal point and circle around it while holding it as the axis point.
The second method of seething is much more adaptable to any situation, although it may not be as historically accurate. It entails the raising of great emotion and force of Will through the act of rocking back and forth, or clenching and unclenching the muscles of the body in rapid succession. It is from this method that we gain the modern usage of the word “seething”, as in: “I was seething with anger”.
Anyone who has “zoned out” while relaxing in a rocking chair can understand how this method works. By simple rhythmic control of the animal body the mind becomes free to wander as it will. By adding a strong emotional component to the movement the mind keeps its focus on the magical work being done and the Power is raised. This technique of seething is very similar to the Gardnerian Wiccan practice of ritual scourging to raise the power, as it both controls the blood flow and heightens the emotional state.
If a witch becomes proficient in this form of seething to raise the Power she may be able to seethe simply by controlling her breathing and clenching and relaxing certain muscle groups in the body. This practice is very akin to raising kundalini, the serpent energy in the base of the spine. Witches known about this serpent energy for ages, and it is thought by some researchers that the so-called Osculum Infame, or the kiss given to witches in fidelity to the Devil on his backside, was simply another way to raise this latent energy.