The Great Cycle of Magic describes the endless flow and transformation of sorcery through the Mortal Realms, the cosmic process by which the eight winds of magic rise, spread, and return. When the world of the old legends was destroyed, its magic did not vanish but separated into eight distinct winds, each of which condensed into a realm of its own, and the interplay between these energies underlies all enchantment in the setting.
Magic in the realms is elemental and tied to place. The fire-magic of Aqshy burns hottest in its home realm and thins the farther it travels; the death-magic of Shyish pulls all things toward endings. Spellcasters draw upon whichever wind is strongest around them, so that the same incantation may blaze in one realm and sputter in another. Mastering the local wind is the first lesson of every wizard.
The cycle is not static. Winds bleed across borders, mingle at the edges of realms, and can be dammed, redirected, or catastrophically unbalanced, as Nagash attempted when he tried to bend all magic toward death and instead unleashed a realm-shaking disaster. To understand the Great Cycle is to understand that magic in this age is not an abstract force but a living, moving current, one that shapes the land, the seasons, and the fates of everyone who dares to wield it.