Chaos Gods

The Chaos Gods, also called the Dark Gods or the Ruinous Powers, are powerful beings of the psychic dimension that underlies all physical reality known as the Immaterium or the Warp, created and sustained by the emotions and collective desires of every sentient being of the material universe. Although they are god-like beings, they are by their nature monomaniacal and completely single-minded since they are formed completely of a single emotion or concept as well as being completely dependent on the emotions of mortal creatures, especially the hordes of humanity, for their power and continued existence. As a result, the Chaos Gods strive to convert all mortals to their worship and service so that they may ultimately dominate all the universe, though if they were to do so it would likely destroy all reality as the dimensional separation between the physical universe and the Immaterium broke down. The Chaos Gods and the Forces of Chaos that serve them are the greatest enemies of the Imperium of Man, the Eldar and most other sentient forms of life in the Milky Way Galaxy, even if they are not fully aware yet of the threat Chaos poses, like the Tau Empire. The Chaos Gods are able to devote a fraction of their psychic power in the Warp to create daemons, whose appearance and character reflect their patron God's own nature. These daemons may be reabsorbed into the God at their whim. The least of the minor Gods may be so limited in their power that expending that power to create a daemon means their entire power is expended; in effect, the God becomes a daemon.

Overview
The Chaos Gods are the supernatural rulers of the Immaterium (the Warp) and have a great impact upon the events occurring in the physical universe. The most powerful of the Chaos Gods includes Khorne, the God of Warfare, Violence and Murder, Nurgle, the God of Disease and Decay, Tzeentch, the God of Change and Sorcery and Slaanesh, the God of Pleasure and Pain. There is a fifth Chaos God named Malal who embodies Chaos' tendency to turn in upon itself and who acts against the interests of the other Chaos Gods whenever he can. Occasionally, the Chaos Gods can set aside their innate rivalry and unite in the pursuit of a larger goal, such as the overthrow of the Imperium of Man which represents the forces of Order in the Milky Way Galaxy. During this time, the forces of the Ruinous Powers can be considered to serve a concept known as Chaos Undivided. The Ruinous Powers generally draw their strength from the sentient minds of the Milky Way Galaxy's inhabitants, whose collective unconsciousness shapes the psychically-reactive substance of the Immaterium and actually gives birth to the Chaos Gods and any other spiritual entities who are empowered by a sufficient level of belief, like the Eldar's lost Gods or the Emperor of Mankind himself. The Ruinous Powers possess the ability to interact with the material universe in a limited way as the entities of the Warp can at times enter the material universe through the minds of those individuals gifted (or cursed) with psychic powers. The Ruinous Powers can also shape lesser supernatural entities from the psychic substance of the Warp who are lesser extensions of their own wills and are generally referred to in the Imperium of Man as daemons. The Tau are generally excluded from worrying about possession by Warp entities like daemons because of their limited psychic abilities and thus their limited presence in the Warp. The Necrons, as intelligent yet souless creatures composed of living metal, also no longer project any psychic presence in the Warp, while their C'tan masters are beings purely of the material realm who are unusually vulnerable to psychic attacks because of their lack of a presence in the Immaterium.

Origins
In the early history of the galaxy, the powers of the Warp had yet to form into distinct, intelligent entities. At this time, the emotions of sentient mortals flowed and ebbed as water does in a stream. As the intelligent mortal races grew and prospered, so did the strength of their emotions. Eventually, the Gods grew to such a point where they could act independently of the general flow of emotions and thus became the Gods of Chaos. They reached into the dreams of mortals and demanded praise and servitude in order to increase their own power, as the more one emotion is exhibited (in both thought and action) by a large group of sentient beings in the physical universe, the stronger that Chaos God becomes.

The four primary Chaos Gods are:
 * Khorne, The Blood God - God of War, Murder, Battle - Khorne is the Blood God, an angry and murderous God of Chaos whose bellows of limitless rage echo throughout the corridors of time and space. His great brass throne sits upon a mountain of skulls in the midst of a plain of splintered bone and lakes of mortal blood formed from the remains of his followers salin nattle and those who his minions have killed in his name. Khorne embodies mindless and absolute violence, destroying everyone and everything within reach, shedding the blood of friend and foe alike. The followers of Khorne are always ferocious warriors and never make use of psychic powers, for the Blood God abhors the trickery of magic and cowardly sorcerers, particularly the servants of Tzeentch. Men turn to Khorne for the power to conquer, to defeat their enemies in battle, to wreak bloody vengeance and to attain unmatched martial prowess against all comers. The most fanatical and dedicated of his followers, those whose souls are trapped fully within his bloddy embrace, know that he truly desires only constant and wild slaughter for its own sake. Khorne cares not from where the blood flows, only that it flows without cease for all eternity.
 * Tzeentch, The Changer of the Ways - God of Change, Sorcery, Fate and Hope - Tzeentch is known by many titles across the galaxy, including the Changer of the Ways, the Master of Fortune, the Great Conspirator and the Architect of Fate. He is the Great Sorcerer, the God of Sorcery and Change and master of the mutable stream of destiny and time. Tzeentch is, without question, the most disturbing and least comprehensible of all the Chaos Gods. His skin crawls with constantly changing faces that leer at and mock all who look upon him. Whem Tzeentch deigns to speak to other beings, these faces repeat his words, often with subtle but important differences of intonation and meaning. Plotters and schemers find themselves drawn to Tzeentch, especially those who crave psychic or sorcerous power to achieve their goals. Politicians and leaders, magisters and Chaos Cultists, all find themselves drawn along the convoluted oaths of fate, using Tzeentch to achieve their dreams and aspirations, though ultimately all are led to play their part in Tzeentch's own eternal schemes. No man can fully comprehend the full nature of the intricately-woven, multi-layered plots of Tzeentch and to attempt to do so can only lead to insanity. Yet in reality Tzeentch has no grand plan, no ultimate goal to fulfill. For Tzeentch the mere act of plotting and entwining the brief fates of mortals is purpose enough. There is no end to his scheming for he desires no end to the creation of change. Tzeentch can never achieve any ultimate aim for to do so would be the end of ambition and thus the end of the Lord of Destiny.
 * Nurgle, The Plague Lord - God of Death, Disease and Decay - Nurgle is the mighty Lord of Decay who presides over all physical corruption and morbidity. Disease and putrefaction, the inevitable entropic decline of all things, are the favours he bestows upon the universe. The God's immense body is bloated with corruption and exudes a sickly, diseased stench. His skin is greenish, leathery and necrotic, its surface pock-marked with all of his various boils, running sores and favorite infestations. From his exposed guts spill tiny Lesser Daemons, his Nurglings, who dine upon the filthy fluids that ooze from Grandfather Nurgle's many festering wounds. It is to free themselves from despair -- the eternal mortal dread of disease, starvation and death -- that men turn to the Plague Lord. Despite his appearance, he is a warm, welcoming God who prides himself on the achievements of his followers, gifting them with his most hideous diseases even as he protects them from all pain and the cold sleep of death. The fear of death can be found in the hearts of all the sentient beings of the universe, and so there is no shortage of mortals willing to sacrifice their immortal souls in return for the corrupted preservation of their physical bodies for all time.
 * Slaanesh, The Prince of Pleasure - God of Pleasure, Sensation and Desire - Slaanesh is the youngest of the Chaos Gods and alone of all the Ruinous Powers, the Prince of Chaos is divinely beautiful. He is as seductive as only an immortal can be, disarming in his innocence, utterly beguiling in his manner and irresistably tempting with his words. Slaanesh can assume male, female or hermaphroditic form at will and it is impossible for a mortal to look upon him without losing his soul and becoming a slave to the Prince of Pleasure's slightest whim. Mortals that seek charisma and fellowship turn to Slaanesh, for his gifts can make one popular and inspiring. Poets and artists are drawn into his gaze by the promise of inspiration and fame, while even the hardiest warriors might seek the adulation of the masses and the ironclad loyalty of their followers. Yet as one continues in the service of Slaanesh, such pleasures soon grow stale and his servants are driven on to search for ever greater sensations and ever more self-fulfillment until only the most decadent and debased of acts can stir their emotions or provide the pleasure they have come to crave.

The first three Chaos Gods became sentient by the middle of the 2nd Millennium, but Slaanesh did not fully awaken until the Fall of the Eldar in the 29th Millennium at the end of the Age of Strife.

There is a fifth major Chaos God who appeared in earlier editions of Warhammer 40,000 but who is almost never mentioned save by the most arcane of texts:
 * Malal/Malice, The Renegade God - God of Anarchy, Vengeance and Nihilism

Followers
The Chaos Gods' most devoted and powerful mortal followers are known as Champions of Chaos, and are spiritually bound to their patrons. Chaos Champions are rewarded with the Mark of their patron Chaos God, mutational or psychic "gifts" unique to each God and the potential blessing of ascension to become a Daemon Prince of that God. When a follower of a Chaos God dies, their soul is absorbed into the greater psychic mass of that God within the Warp, adding its energy to the already formidable power of that God. It is for this reason that the Ruinous Powers seek to corrupt and turn to their worship as many mortal souls as they possibly can.

Daemons
A daemon is a creature formed from a fragment of a Chaos God's consciousness. They form the armies of the Chaos Gods within the Warp, and frequently battle the daemonic armies of other Gods and unbelievers on the material plane.

The Great Game of Chaos
The Chaos Gods are rivals of each other - the constant war between them mirrors the struggle between their followers in the material universe, and vice-versa. Victory in mortal battles lends more power to the relevant God, although often victory is not necessary, just the shedding of blood and sacrifice is required. The Chaos Gods are almost constantly at war with one another within the Warp, vying for power amid the immaterial planes. Despite their myriad differences, the Great Gods of Chaos have the same goal: total domination. Such absolute power cannot be shared - especially amongst Gods. This struggle for dominance over the Warp and the physical universe by the Chaos Gods is known as the Great Game.

Minor Chaos Gods

 * Ans'l, Mo'rcck and Phraz-Etar are minor Chaos deities. Chaos Space Marines were rumored to praise them by putting spikes on their Power Armour. Their names are puns on the last names of Bryan Ansell, Michael Moorcock, and Frank Frazetta, writers and artists whose work all contributed to the look and feel of the Warhammer Fantasy and Warhammer 40,000 universes.
 * Malice is an entity worshipped as the Renegade God of Chaos and the Hierarch of Anarchy and Terror. The Renegade Space Marines Chapter the Sons of Malice are among his followers. Malice may simply be another version of Malal.