Chaos God

The Chaos Gods, also known as the Dark Gods, are eldritch interdimemsional god-like beings from the Chaos dimension.

Background
The Chaos Gods are entities of great power which rule the psychic dimension beneath the physical universe, which is known as the Immaterium. Beings which were created by and continue to be sustained by the collective emotions and desires of every sentient in the universe. Beliefs or emotions that grow strong enough in the physical universe, result in the creation of their sentient embodiments in the Immaterium. The greatest and most malevolent of them are the Gods of Chaos. Single-minded monomaniacal beings who embody a single concept or emotion, and are therefore dependent on the mortals' emotions for not only their powers but their existence too. Because of this, converting mortals into their worshipers is their primary if not sole goal, with universal domination the prize. Daemons are psychic entities which they've created, whose character and appearance are reflections of their maker's nature. Which can be reabsorbed back into their god at any time.

Milky Way Galaxy
The forces of the Chaos Gods have established beachheads in the Milky Way galaxy. Beachheads that are increasing in number and growing in size. Whole sectors and regions have fallen to Chaos, most infamously the Eye of Terror. Which is a permanent Warp storm and massive Warp rift 20,000 light years long, located to the galactic northwest of Earth. It was the Chaos Gods who were responsible for the tragedy that has befallen the human race, with the God Emperor of Man an undead sovereign and the transformation of the empire into a totalitarian, fascist, theocratic, superstitious, feudal, and technologically stagnant dominion. They are one of the primary threats to the Imperium of Man, alongside the ravenous Tyranids, the machines of the Necrons, and the warlike Orks.

Armies of daemons have conquered or destroyed worlds, uprisings by armies of chaos cultists have seized control of worlds or being crushed after much loss of life, and other chaos cults undermine and corrupt societies from the shadows. In addition whole chapters of the elite superhuman Space Marines (the Chaos Marines) have defected to Chaos, as well as entire worlds of the Adeptus Mechanicus (the Dark Mechanicus), legions of Imperial Guardsemen and Titans, and fleets of the Imperial navy. Many alien races have also fallen to the influence of Chaos, resulting in the destruction of some while others continue to serve Chaos. The least fortunate of their servants are reshaped into the dreaded Chaos Spawn.

List of Chaos Gods

 * Tzeentch: The Architect of Fate, who uses powerful sorceries to alter the future. He was once the greatest of the Chaos Gods and is potentially the most powerful. He's the God of Change, who endlessly plots and schemes, in a cosmic-wide game of subterfuge and manipulation. He became fully sentient in the 2nd millenium, due to mankind during Earth's medieval period. Tzeentch listens to the hopes of all mortals, feeding on their need and desire for change.
 * Khorne: The Lord of Battle, a towering being of fury. He is the Blood God, whose domain is sentients' most brutal and basic emotions and actions, whih are anger, hate, war, rage, and killing. He is empowered by every act of murder in the cosmos, the more destructive and senseless the better. Khorne became sentient during the 2nd millennium, due to mankind during Earth's medieval period. It's his goal to drown the cosmos in a tide of slaughter, until there is only shattered bones and spilled blood.
 * Slaanesh: The Dark Prince of Chaos, who indulges in excess and pleasure, no matter how perverse or immoral. Who is the youngest of the major Chaos Gods, achieving sentience in the 30th Millennium due to the excesses of the Elder. The Prince of Pleasure is dedicated to pleasure and hedonism, seeking to overthrow decent behavior. He approves of excess in all forms, from lust to gluttony to megalomania.
 * Nurgle: The Lord of Decay, who works tirelessly to spread his pestilence and infections. He is the Plague God, empowered by the emotion of despair among mortals. Of all the Chaos Gods, he is the one that involves himself most directly in the affairs of mortals, especiall humans, due to their fear of death. Nurgle became fully aware in the 2nd millennium, due to mankind during Earth's medieval period.