The symbol of The Black Order is two Iwaz runes representing the yew Tree of Life and Death, crossed to form the Cosmic Wheel, surrounded by the self-devouring Serpent. The whole is representative of the evolutionary interaction of polarities.
The yew is associated with Midwinter and is representative for eternal life, yet it is poisonous. In hot weather it gives off a resinous vapour, which shamans inhaled to gain visions.
The basis of evolution is found in entropy, which is the destructive force of Nature. This force is often symbolised by the serpent consuming its own tail, Ouroboros, a being which is both creator and destroyer. The self-devouring world serpent (Iormungand) is thus a universal archetype for the entropic force within the circle of Creation-Destruction-Renewal.