Witchsight

Witchsight is the ability of most spellcasters to sense the presence or absence of Magic. All people born with the talent to work magic have some degree of witchsight that can be developed and expanded with training so the spellcaster can actually see the ebb and flow of the Winds of Magic, witness the scintillating colours of the Chaos energy in its raw form, and be better able to harness it for the casting of spells.

Overview
Sometimes referred to as the seventh sense, Witchsight is the term widely given by Collegiate Magisters to the ability to actually see the Winds of Magic. In some ways, this term is negative, as no trained Magister would ever accept being called a witch and certainly do not consider themselves as such. However, the term is older than the Colleges themselves and has entered the common vernacular of most Magisters alongside less degrading terms such as “spirit-sight.”

Any person possessing witchsight sees the world as if through two types of vision superimposed upon each other. With his normal mundane sight, the Aethyrically sensitive person sees like any other Human does. With his witchsight, the person actually sees the Winds of Magic to some degree, either as swirling clouds and rivers of churning coloured energy, or as manifestations of their own thoughts, memories, emotions, expectations, beliefs, and fears and those of the people around them. The common expression of witchsight in untrained magic users is as strange shapes and flickering lights just at the corner of their vision. Depending upon how strong one’s witchsight is, one may be able to see the movements of magic and magically charged items and beings, even in the dark or if one’s eyes are shut, blinded, or missing.

Some people with the most developed witchsight are able to see the entire world even without their eyes, perceiving with perfect clarity the souls, thoughts, and intentions of all living beings around them, seeing how magic swirls around and through them and all other things in the world. Witchsight may never be turned off and even the greatest Magisters with all their discipline have trouble ignoring it. This is part of the reason why Magisters and other magic users with witchsight are so eccentric, if not plain mad. Those with it are surrounded by a world of swirling magical colours, plainly visible thoughts, dreams, and nightmares, flashes of future and past events, auras, and any number of other arcane and bizarre visions.

Unlike Sixth Sense or Aethyric Attunement, witchsight (or Magical Sense) cannot simply be explained away as just a feeling. It is either considered madness by most people of the Empire, or else people with the witchsight actually believe they are seeing physical things existing around them. Those who were born with witchsight grew up believing that seeing coloured auras around living creatures is entirely normal—they may also be convinced by family and friends who do not posses a similar talent that they are haunted or tormented by Daemons. In a sense, these friends and families are correct, for these things do exist almost everywhere, although these things are almost never visible and can only very rarely interact with the mortal world.

Apparitions & Harbingers
Having the ability to sense magic enables Magisters and their ilk to better control the energies they wield. Aside from its utility, witchsight also reveals an abundance of odd manifestations, eerie phenomena, and sometimes glimpses of the future and the past. Most Magisters learn to cope with the sometimes unsettling visions they experience, reminding themselves that their art is one of mysteries that are impossible to unravel. But some phantasms are too frightening, too maddening to ignore. These are the vestiges, the essence of Chaos formed into something that resembles flesh, but is intangible, insubstantial, and can affect the world in no significant way—or so the Magisters say.

The things of the Aethyr, for lack of a better term, are harbingers, apparitions foretelling some significant event. They may take the form of a nest of wriggling maggots, the fiery forms of long-dead witches, or even a pack of ghostly hounds that breathe fire and shower sparks wherever they step. Despite their macabre and disgusting appearance, they seem to have no power over those who see them.

So, what then, are these things that only those with witchsight can see? There are many theories, ranging from Daemons struggling to breach the barrier between the world of men and the Realm of Chaos to hallucinations brought on as a result of dabbling in the forbidden. What is known for certain is the apparitions always appear in the aftermath of some significant magical event, as if they were drawn to the instance, somehow compelled to witness the caster in his act of magic use. More importantly, the same harbingers tend to appear time and again when certain conditions are met. For instance, the Handmaidens always manifest themselves after excessive use of Gold or Celestial Magic. The Rotwyrms seem drawn to Jade and Amethyst Magic, and so on. Since these apparitions appear again and again, there must be some reason for their appearance, and they must fulfill some purpose.

Source

 * Warhammer Fantasy RPG 2nd ED -- Realms of Sorcery (pg. 46-47).
 * Warhammer Fantasy RPG 2nd ED -- Tome of Corruption (pg. 207).