Chaos Sorcerers are powerful spellcasters who use the raw Winds of Magic to cast spells and unleash Chaos Sorcery.

Those Champions of Chaos who seek mastery over the magical arts are known as Chaos Sorcerers, and they are madmen and malcontents all. They are amongst the most awful and depraved of all servants of the Ruinous Powers, for they long ago sold their souls in exchange for the heady elixir of pure power. Where many of the Known World's wizards, such as those taught by the Colleges of Magic in Altdorf, glean their arcane skill from long years of painstaking research, a Chaos Sorcerer's understanding of the Winds of Magic is often instant and innate. Without the patience and wisdom that such study brings, an inexorable descent into deformity, mutation and madness is nigh on inevitable.

Chaos Sorcerers are masters of Dark Magic, and there is little beyond their might. They can transport themselves over vast distances, call upon the fires of Tzeentch, slaughter men by the scores, and more. But such magic comes at a terrible price. As they tap the energies of Chaos, their sanity withers whilst their bodies twist and mutate with the invoked energies.

Chaos Sorcerers may be found amongst the savage tribes of the Men of the North, serving as oracles and counsellors, but many also come from the civilised lands of the Empire and beyond. These individuals, finding the limitations on magic within the Imperial Colleges of Magic too restrictive, and lured by the power to be held by dabbling in daemonology, drift north to bring themselves closer to the source of their magic in the Chaos Wastes, learning through trial and error.

What separates Chaos Sorcerers from other spellcasters, namely the Magisters of the Empire, witches, and warlocks, is that these individuals derive their power directly from the Chaos Gods. Thus, only mortal servants of Nurgle, Slaanesh, and Tzeentch may become Chaos Sorcerers. There are no sorcerers of Khorne, for the mortal servants of the Blood God abhor the use of magic as the weapon of cowards, like their divine patron.

According to Magister Patriarch Verspasian Kant, Chaos Sorcerers benefit from the guidance of their chosen Chaos deity, similar to a practictioner of Divine Magic, channeling and focusing the unbridled potentiality of the Aethyr through their Dark God rather than drawing upon the Winds of Magic directly. As such, the magic of a Chaos Sorcerer bears unique traits that are otherwise non-existent or unachievable using more usual methods of spellcasting.

Source: https://warhammerfantasy.fandom.com/wiki/Chaos_Sorcerer

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

A sorcerer or Chaos Sorcerer is the most powerful type of psyker found among the Chaos Space Marines and the other mortal forces of Chaos.

Sorcerers serve the same role as Librarians do for Loyalist Space Marine Chapters and Sanctioned Psykers do for the Astra Militarum, though many powerful sorcerers can also be considered psychically-gifted Champions of Chaos and Sorcerer Lords.

Instead of the subtle psychic manipulation and divination used by the Farseers of the Aeldari or the strength-boosting powers of the Space Marine Librarians, the sorcerers of Chaos wield death, destruction, and mutation, the mightiest powers of the Warp.

Sorcerers of Chaos shape destiny itself with arcane rituals and unspeakable pacts forged with the malefic entities -- the Daemons -- of the Empyrean. In truth, "sorcery" itself differs from other forms of psychic ability because it requires interacting and cutting deals for knowledge and/or power with the entities of the Warp in the pursuit of one's own selfish gain.

Through the knowledge gained by such pacts, sorcerers channel the soul-blasting energies of the Warp into potent hexes and blasts of wyrdflame, and they mould the fabric of the material universe with little more than a hate-filled curse.

Because of their constant exposure to the power of Chaos, sorcerers are inevitably haunted by the prospect of eventually succumbing to crippling mutation or insanity. Though they believe they are above mortal concerns, the truth is that they, too, are only pawns, raised up and then expended by the Dark Gods for their own amusement.

The line between wielding psychic power and true "sorcery" is a fine one indeed. The Chapters of the Adeptus Astartes may seek to deny it, but every time a Space Marine Librarian calls upon his mental might he risks tainting his soul.

In the heat of battle, even the most capable psyker may overreach his abilities, and instead of recoiling in horror from the resultant carnage, he may feel a forbidden thrill. Such emotions are the first step on a path to limitless evil.

From that moment on, the psyker may endure honeyed whispers in his dreams and visions of immortality. Those who succumb to such temptations and make deals for power with the Daemonic denizens of the Immaterium become true sorcerers, able to channel the malefic power of the Warp to its fullest extent, unconstrained by morality or consequences.

Sorcerers are forever driven to expand their influence and knowledge. They see themselves as having ascended; no longer hindered by blind loyalty to the Corpse-God of the Imperium, they become even more callous and inhuman than those who follow them.

Some are cold-hearted strategists who vent their hatred upon as much of the universe as possible; Ygethmor the Deceiver once orchestrated a doomsday cult that resulted in the depopulation of every inhabited world in the Corriallis System.

Others act as advisors for Chaos Lords, subtly redirecting them to their own ends under the illusion of servitude. A rare few roam the hidden paths of the universe, unlocking the secrets of the ancients to better plunge the galaxy into the embrace of Chaos.

Regardless of their goals, all sorcerers revel in the anarchy of the Long War. It takes only a flicker of resistance to spur them into unleashing the destructive energies of the Immaterium. Their bitterness manifests upon the battlefield as a palpable force; red-hot skulls hammer down from the skies, disease chokes the souls of those nearby, and men are turned into monsters in their wake.

The martial prowess common to all Chaos Space Marines is magnified greatly when combined with the weapons of the sorcerer, baleful artefacts saturated with the energies of Chaos that can rip the soul from the body of their victim.

The Thousand Sons Legion gave rise to the first Space Marine sorcerers during the early days of the Great Crusade. Even before the Horus Heresy, the XVth Legion of Magnus the Red had a thirst for knowledge of the Warp that proved impossible to slake, and ultimately proved their undoing.

In his arrogance and ignorance, Magnus ignored the warnings of his father the Emperor and could not stop himself from dealing with the denizens of the Warp in the search for ever more knowledge about how to enhance and extend his psychic abilities and those of his Astartes.

Without even realising it, he struck a pact with the Chaos God Tzeentch that ultimately resulted in the damnation of himself and his Legion. Most of the Thousand Sons' number were ultimately reduced to unliving automatons by the Rubric of Ahriman, though the most psychically powerful among them were able to resist the unforeseen consequences of that grand ritual.

Many of these ancient sorcerers have now forged pacts with Abaddon the Despoiler, joining the Warmaster of Chaos in his quest to overthrow the Imperium of Man and adding the strength of their Rubricae bodyguards to that of the Black Legion.

Source: https://warhammer40k.fandom.com/wiki/Sorcerer