C'Thun (pronounced "Kah-Thoon" or "Kathune") is the final boss in the Temple of Ahn'Qiraj. Until the release of the original Naxxramas and later The Burning Crusade, C'Thun was considered the most difficult raid boss in the game.
In its first inception, C'Thun was considered to be unbeatable with the current level of gear. However, following a number of hot fixes, phase two was made considerably more controllable, and the first kills were registered in a matter of hours following one such hot fix.
Before the Ordering of Azeroth
As one of the five Old Gods - who are known to be among the most powerful beings that ever walked Azeroth - C'Thun ruled over the young world. Azeroth was overwhelmed by elemental storms and the Old Gods held tyranny over it. 
Along the journey of the Titans they happened upon Azeroth. As the Titans made their way across the primordial landscape, they encountered a number of hostile elemental beings. These elementals vowed to drive the Titans back and keep their world inviolate from the invaders' metallic touch. The Pantheon, disturbed by the Old Gods' penchant for evil, waged war upon the elementals and their dark masters. Though the elementals were powerful beyond mortal comprehension, their combined forces could not stop the Titans. One Old God was killed during the battle and its remains can be seen at the Master's Glaive in Darkshore with an immense sword piercing its skull. Three were weakened while C'Thun fell into the barren lands of Silithus - but didn't die.
The Pantheon shattered the Old Gods' citadels and chained the surviving three evil gods far beneath the surface of the world. Without the Old Gods' power to keep their raging spirits bound to the physical world, the elementals were banished to an abyssal plane, where they would contend with one another for all eternity. With the elementals' departure, nature calmed, and the world settled into a peaceful harmony.
Creation of the Qiraji
For countless ages, C'Thun slept and watched as races evolved, fought each other, saw invasion of the Legion and still, created plans for the future - its future. In the desert into which it fell, C'Thun found primitive life-forms known as the Silithid. The Old God created avatars from the Silithid in its own image. These avatars were to be known as the Qiraji, a sapient race that would come to occupy the western lands of Kalimdor. The great fortress city of Ahn'Qiraj was created to house their growing armies and prepare for the coming of C'Thun.
War of the Shifting Sands
After his children had spent thousands of years building an army capable of exacting revenge upon the whole of Kalimdor the moment that C'Thun had so patiently waited for had finally arrived.
The Titans had long since vacated this world. Only the Night Elves were here to defend. As the whole of Silithus was soon engulfed by the Silithid and their Qiraji hosts the Night Elf army was pushed back through Un'Goro, to the borders of the Tanaris desert. With the aid of the four dragonflights, the Night Elves could finally push the Qiraji back to the city of Ahn'Qiraj. There a barrier was erected out of rock, stone and roots from beneath the sands to create an impenetrable wall. The Qiraji who remained outside the wall were quickly slain.
- Main article: C'Thun (tactics)
Centuries later the Gates of Ahn'Qiraj had been reopened, and the war reached its conclusion. Rumors circulated that C'Thun is present here with its great, horrifying lidless Eye, surrounded by a sea of tentacles and will vaporize every ignorant mortal who thinks of daring to challenge its supreme power and right to the world of Azeroth. So some mortals fought the Qiraji and finally reached the Chamber of C'Thun.
While the Lich King attacked Stormwind City and Orgrimmar and King Varian Wrynn and Warchief Thrall were distracted, Cho'gall began the resurrection of his new master - the Old God C'Thun. This deformed the ogre's body which became monstrous and with similar features to his master's.
C'Thun in the encounter is a composition of different NPCs:
- Eye of C'Thun
- Body of C'Thun
- Eye Tentacle
- Giant Eye Tentacle
- Claw Tentacle
- Giant Claw Tentacle
- Flesh Tentacle
- Stomach of C'thun
Also pointing towards a reference to Cthulhu is the idea of insanity, such as the Dark Edge of Insanity item drop, as well as possibly several of his quotes, such as "Your friends will abandon you", and "You will betray your friends." Cthulhu in H.P. Lovecraft's novels deals very heavily with insanity as well, with both his followers often being described as mad, as well as those who find themselves in the events surrounding him often losing their sanity.
It is likely that the words C'thun, Cthulhu, Cthonia, and C'tan are all derived in some form from the Greek word "Chthonios" (Xθωνιος), which means "under the earth or "inside the earth". Although there was no specific god named Chthon in Greek mythology, the word "chthonic" (sometimes spelled "cthonic") is still used in mythological studies as an adjective to describe earth-related deities. It seems that Blizzard, Lovecraft and Games Workshop adapted the word for their own uses.
While C'Thun bears no striking physical resemblance to artists' renderings of Cthulhu, it is an Old God, possibly similar to the "Great Old Ones" from Lovecraft's novels, of whom Cthulhu is the most prominent (though not the most powerful) member. C'Thun's eye, however, does greatly resemble Tolkien's Eye of Sauron. The eye of C'Thun looks very much like the Dungeons & Dragons god, Gruumsh, the chief-god of the orcs. C'Thun's physical form bears at least some resemblance to the Zerg Overmind of Starcraft.
Resemblance between C'thun and the C'tan is that the old gods fought against the titans, and the C'tan fought the Old Ones. Old Gods and C'Tan are described in a very similar way, as titans and old ones do.
The name Cthun is referenced in the Stephen King short story "N." featured in Just After Sunset. In the story, Cthun is a hidden world of old gods and abominations that is kept at bay by a shifting circle of stones in an abandoned field, where a caretaker must stand watch and, through his perception, constantly "fix" the circle by making sure there are eight stones instead of seven. The rite induces severe OCD-like symptoms in its practitioners, resulting in a string of identical suicides. One of the beings that frequently attempts to pass through the circle is described as an inhuman, three-lobed eye.
C'thun may also be a reference to Elder God from the Legacy of Kain series.
- C'Thun bears a striking resemblance to the Forgotten one beneath Azjol'Nerub in Warcraft III: The Frozen Throne.
The following are audibly whispered to players throughout the raid.
- Death is close.
- You are already dead.
- You are weak.
- You will betray your friends.
- You will die.
- Your courage will fail.
- Your friends will abandon you.
- Your heart will explode.
- It's all fun and games until somebody loses an eye. (removed)
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