Heretic

Heretics or apostates are those believing in or practicing religious heresy, holding beliefs and opinions at odds with that of their former religion or group, and therefore opposed to a set of doctrines and teachings. In fact, heresy is any belief, practice, blasphemy, act, or theory that is strongly at variance with established beliefs, traditions, or customs in a society, in particular the accepted beliefs of a religious organization.

Present among all the races, cults, and societies, those accused of being heretics by their actions and beliefs are denigrated or treated as pariahs by their people, and subsequently rejected, exiled, or eliminated.

The inquisitors are mainly responsible for tracking down the heretics in order to arrest and interrogate them, by torture if necessary. Some extremist organizations, such as the Scarlet Crusade, devote themselves to their eradication, going so far as to throw them into cages and prisons where they are treated like animals, before being cruelly executed.

First War

 * The fel and demonic energy employed by Gul'dan and his warlocks of the Shadow Council were considered as heretical magic.

Third War
Years before the Scourging of Lordaeron, the necromancer Kel'Thuzad began to preach his heretical "religion" through Lordaeron, promising immortality, power, and an ideal society free of all the burdens. Many were those who consequently forsook the Light, willingly selling their soul to the Lich King, and joined the Cult of the Damned.

During the Third War, a group of wretched and heretical fallen priests appeared. They once counted as the most devout amongst the clergy of Lordaeron. But, after years of constant war and suffering, they had lost their sense of the Holy Light. Now, they existed only to spread their frustration and negativity to their fellow men and women.

They appeared as a category of creeps and counted Fallen Priests, Deceivers, and Heretics among their ranks. They were modeled after the Acolytes of the Scourge.

The Sunwell Trilogy

 * The magics dabbled by the elite magic-using sect known as the Highborne, drawn upon the power of the Well of Eternity during the reign of Queen Azshara, were considered heretical by many other elves.

World of Warcraft

 * The Kirin Tor and their magi have been considered heretics for centuries by the Church of the Light who has never been fond of their methods, but let them continue to exist because they don't practice dark magic and are somewhere necessary.
 * The warlocks and their dark arts are considered as pariahs that must operate in the shadows of polite society in order to practice in secret their dark arts within hidden enclaves, so that they can escape the prejudice of the public.
 * Jonathan Carevin and his family have dedicated themselves to fight the undead and worgen of Duskwood in order to repel the evil and heresy in the region.
 * The Centaur Pariah was considered a heretic and exiled by his centaur brethren for his beliefs.
 * The priests and paladins of the Scarlet Crusade were once members of the Church and the Silver Hand. However, they became corrupt and extremist as a result of their fanatical dedication to eradicate the undead, and those who oppose them.
 * Duke Nicholas Zverenhoff of the Argent Dawn tasked an adventurer to slay Archivist Galford and burn down his archives in order to take away the Crusade's most valued documents and punish them for their heretical zealotry.

The Burning Crusade

 * To some draenei, the shamanistic teachings of the Broken were considered heretical.
 * Before becoming blood elves, the high elves of Quel'Thalas were followers of the Church of Light, some as priests and paladins. However, after the Third War, they lost faith and altered the philosophy of the Church, notably by forcibly took their power from a naaru, as the Blood Knights considering themselves the masters of the Light.
 * The Twilight's Hammer cult spread throughout every societies on Azeroth, secretly evangelizing and converting others to their dark cause, notably Archbishop Benedictus and some of his followers of the Light.
 * The naga usually revere Queen Azshara as a demigod, but a group instead worshiped Neptulon, and they were deemed heretics for it. Skar'this led them, and several bodyguards, crystal guards and emissaries appeared during the Midsummer Fire Festival.
 * By his pact with Illidari Lord Balthas, to which he gave his blood, Sar'this owes the latter some favors and is called a arakkoa heretic.

Cataclysm

 * Prior to the Cataclysm, and unable to contact the elements, Muln Earthfury and the Earthen Ring had to decide if Shotoa was a hero or a heretic, as the latter tried to convince them to change their methods, and instead, to force the elements to obey them.
 * Vassandra Stormclaw mentioned that the Curse of the Worgen began as a heresy for the night elves druids during the War of the Satyr, when the Druids of the Pack allowed the beast to overtake them against the Lords of the Emerald Flame. They were later banished to the Emerald Dream because of their dangerousness and to prevent the curse from spreading.
 * Kotonga of the Revantusk tribe considered the dark voodoo of the Vilebranch tribe as heretical.
 * Druids of the Flame were considered heretics by the Shadow Wardens present in the Firelands, some of them were captured at the Forlorn Spire to be questioned and then eliminated.

Mists of Pandaria

 * In the saurok Skumblade tribe, Skumblade Seadragon are held in lower regard, for they keep the shores filthy and hunt in water, which the Skumblade Saur-Priest regard as heretical.

Legion

 * The Bloodtotem allied with the Burning Legion, becoming the Feltotem. They took control of sacred sites of Highmountain for their necrotic rituals, Taurnash the Heretic was among them.
 * The ghost of the vrykul Shieldmaiden Iounn accused the Bonespeakers for their heretical actions, notably raising the dead with their rune magics.
 * In their fall, the Scarlet Onslaught started deeming some of their own as heretics and apostates, locking them in cages like animals, in order to execute them later. Mariella Ward was among them.
 * The Cult of Forgotten Shadows is a group considered heretical by most, who believes that dark energy practitioners are just as vital to the survival of life and reality as wielders of the Light.
 * Over the millennia, the Sisters of the Moon who acted as the guardians of the Temple of Elune, now the Tomb of Sargeras, have been corrupted to madness. They have since considered any intruder as heretics to be eliminated.
 * In one of the visions of a possible future, shown by the Void, Alleria Windrunner saw Xe'ra declaring her a heretic and calling for her death.

Battle for Azeroth

 * The followers of Zul were considered heretics.   The Zandalari trolls who later rebelled against the rule of Queen Talanji were also considered as such. This may refer to the Zandalari royalty title of "God King".
 * Brother Alen of the Tidesages was considered a heretic by Lieutenant Wade when he reported the situation of the Kul Tiran fleet to Taelia Fordragon and an adventurer. His corpse was later found hanging from an arch behind the Stormsong Monastery, killed by the Stormsong loyalists.
 * Shandris Feathermoon ordered the purge of the naga from Elun'alor Temple, accusing Azshara and her minions of having defiled for too long the ruined temple of Elune with their heresy.

Shadowlands

 * Ages ago in the Shadowlands, Zovaal betrayed his fellow Eternal Ones, attempting to steal their sigils in order to access forbidden knowledge. He was then condemned for his heretical actions by being imprisoned for eternity in the Maw.
 * In Revendreth, those who claimed Denathrius to be responsible for the anima drought were considered heretics by Lord Chamberlain. The latter is also at the head of a Venthyr Inquisition, which torments the souls under their care and hunts down those who oppose Denathrius.

Others

 * Named
 * Crazzak the Heretic
 * Darkscreecher Akkarai
 * Terokk
 * Vakkiz the Windrager


 * Unnamed
 * Heretical Warmother
 * Shadowsworn Heretic
 * Twilight Heretic


 * Heretic Temple Priest
 * Zandalari Heretic

Items

 * Apostate's Hauberk
 * Binding of Dark Heresies
 * Heretic's Gauntlets
 * Slippers of the Forgotten Heretic

In the RPG
The Heretics of the Holy Light include the Argent Dawn and the Scarlet Crusade. These are religious groups that altered the holy light philosophy and splintered from the Church of the Holy Light.

Of the two splinter factions of the Church of the Holy Light — the Argent Dawn and the Scarlet Crusade — the Argent Dawn is by far more palatable to the Church. Still, both technically go against the church's established teachings to blaze new paths.

The Argent Dawn believes the church’s old methods of dealing with evil no longer suffice. Evil constantly changes and refines its methods, and good must likewise change. The Scarlet Crusade takes this notion one huge step forward. The crusade rationalizes that evil has no restraints on its tactics, and neither should good if it expects to triumph. While both groups go against the teachings of the Church of the Holy Light, the church takes no direct action against them. This lack of activity on the church's part derives from its unique structure. While it is the dominant faith among humans, the Holy Light is not a religion so much as it is a philosophy. The "church" is a network of the faithful that exists to bring worshipers together and provide new members with guidance. Adherents to the path of the Holy Light don't attend services once a week or build edifices to celebrate their philosophy (with a few exceptions). Plus, the Church of the Holy Light — and its adherents — have larger problems to worry about.

In addition, while their doctrine might be radical, none can deny that the Argent Dawn and the Scarlet Crusade accomplish what they set out to do. The Argent Dawn has become the preeminent enemy of evil in some areas, and the Scarlet Crusade deals blow after vicious blow to the Scourge. While their methods may be questionable (particularly in the case of the Scarlet Crusade), their accomplishments dissuade most faithful of the Holy Light from interfering.

Domains: Priests of the Holy Light who serve the Scarlet Crusade can gain access to the Crusader, Healing and War domains (but not Protection).

Notes and trivia

 * While they considered them as heretics in the non-canon Warcraft RPG, according to Chris Metzen, the Church of the Holy Light fully supports the Argent Crusade and hates the Scarlet Crusade.

Speculation
The Heretics that could be found in Warcraft III on Kalimdor right after the arrival of the Horde and Alliance may have represented Twilight's Hammer members.