Earthbound Magic

Each of the Winds of Magic flows around the world. Their powers and influences wax and wane in strength as they move, depending upon what they come into contact with. Each of these Winds disperses in a subtly different way from the others, some quickly and thickly, others slowly over wide areas. They are often drawn to or repelled by different things, sometimes creating hotspots of magic (like the Athel Loren), and other times creating null-zones where there is almost no magic at all.

Whatever their patterns of dispersal, the Winds of Magic permeate and are absorbed into almost everything in the world with which they come into contact. The degree of this absorption and its effect varies hugely depending on the particular Wind in question and the object or thing it is permeating.

Living tissue can absorb considerable amounts of Aethyric energy, while other materials (sometimes lead, others obsidian) are magical nulls. So with this exception, almost everything that the Winds of Magic touch is saturated by their power to some degree or another, creating an ambient hum of magic everywhere in the Old World. a

The closer one travels towards the Chaos Wastes and the source of the Winds of Magic, the greater this saturation becomes, and the more obvious its effects upon the mortal world. Mutation is rife amongst creatures and plants. Nature itself is warped and changed and the very physical laws that govern reality begin to break down. Worst by far, the more magically saturated the environment, the more frequent and profound are the physical manifestations of various Chaos Realm entities. The further one travels from the world’s poles towards equatorial regions, the weaker the ambient hum of magic becomes. b

There is no upper limit on the amount of magic a physical thing can be saturated with. A tree could absorb a certain degree of magical energy without any noticeable effect, but if this absorption continued, the tree would start to manifest supernatural traits. It may start to produce fruit or flowers where it never had before. In time, these fruits and blossoms might become endowed with diverse magical properties. If the level of magic in the area continues to increase, and the tree absorbs more magical energy than it loses to the suction of the Great Vortex, it might start to manifest even wilder supernatural traits like mobility or even self-awareness. Eventually, the tree will start to lose any stable physical coherence and dissolve into a churning mass of constantly shifting matter and energy.

This does not mean everything the Winds of Magic touch has the capacity to store magic indefinitely. All magic leaks slowly out of all things as it is drawn away by the Great Vortex in Ulthuan. This Vortex is the only thing that stops the world from becoming so saturated with magic that it becomes an extension of the Chaos Wastes, or even just a wider portal to the Aethyr itself. The reason the northern Chaos Wastes remain eternally warped and bizarre is because the Winds of Magic blow so strongly and consistently there, perpetually renewing the amounts of magical energy that saturate the environment far more quickly than the Vortex can draw away.

While there is no maximum quantity of magic that a mundane object might be able to contain, there is no guarantee that the permeating magic will stay until tapped into by a magic user. The magic permeating something can drift/leak/be drawn away by a proximity to leylines, henges, and the Great Vortex. The level of magic left in most physical objects, areas, and things will gradually lessen if the Winds do not blow over and through them regularly.

Only items that have been especially prepared and manufactured by skilful Magisters or Runesmiths are able to store magic safely for any length of time. Indeed this is the whole basis of runecraft and what makes it so special—it can attract and store the Winds of Magic with excellent stability and for long periods. With mundane things like grass or rocks, magic can drift out just as easily as it drifts in. Runes, on the other hand, are designed to store magic within the item they are carved upon. The runes only release the magic under the direction of the wielder and only according to the parameters of the runes storing the magic.

Because mundane things like grass generally have a very low ambient saturation of magic, it is exceedingly difficult for a magic user to draw enough energy out from them to power anything but the most minor of spells. Additionally, once ambient magic has been drawn out of the surrounding environment (as opposed to directly from the Winds themselves), it takes a while for that mundane object to be resaturated. c

Source

 * Warhammer Fantasy RPG 2nd ED -- Realms of Sorcery pg. 39 40 41