Magic in the Empire
"Magical abilities mark you as a figure of terror and awe in the Empire. Prior to the establishment of the Colleges of Magic in Altdorf, those able to wield magic were reviled outlaws. Nowadays being a witch is not illegal, but casting magic without a licence is. Spellcasters within the Empire must either study at the Colleges of Magic, refrain from casting spells, or hope no-one notices their illicit activity. Even licenced wizards are generally feared and avoided — legal status has done nothing to reduce the superstitious dread of the common folk. Magic is seen as unnatural and is notorious for its darker elements: the crippling hexes of witchcraft, the raising of the dead, and the summoning of Daemonic entities. Even when practiced according to the teaching of the Colleges, magic can be the cause of trouble. The very source of magic is unstable, and even the most experienced spellcaster can lose focus, resulting in dangerous accidents and unexpected side-effects." Extract from WFRP 4e Rulebook
The use of magic was legalised in 2302 IC by Magnous the Pious when a high elf mage, Teclis, taught rudimentary spells to fugitive wizards to fight Chaos during the Great War. Following Magnus' crowning, the elf founded the colleges of magic where humans could be trained to control their talent.
Magic itself remains a mystery, although it is derived from Chaos, and divided into eight winds. As humans are vulnerable to corruption, they cannot control all eight of them; however, Teclis deemed them capable of mastering a single Lore at the time. This lead to the creation of eight colleges, one to study each Lore associated to a wind. These are the Lore of Light, Metal, Life, Heavens, Shadows, Death, Fire and Beasts.
This is just a quick note, of course things are much more complex in the books ! Feel free to reach out if you'd like to know more on Magic in Warhamme !
Sources : Warhammer Fantasy RP 4e Rulebook and Winds of Magic 4e