The world of Kháos is steeped in ancient myth, drawing from influences such as the MTG setting of Theros (from which this worlds pantheon is derived) and the historical Ancient Greece. But incorporates elements of classical D&D and modern fantasy. Furthermore, unlike Theros and Ancient Greece, the world has moved on from bronze age technology and sits squarely in the medieval ages. But the society emulates the ancient period, with Roman style republics, Greek city states and the occasional kingdom. Feudalism is not widespread, limited only to certain parts of the world, yet threatening to upheave the social order. The gods of Nyx do not only watch from their starry abode, instead always scheming and meddling in mortal affairs to the detriment of other gods. Legendary champions and mythical creatures are made real in Kháos, as the sheer power of belief can make things come true.
Myth Becomes Real
In Kháos, the power of belief is not to be understated - things that are dreamed of here become real. If a local township believes enough in the monster that lurks outside their walls at night, the monster will eventually appear. That does not mean that the monster can simply be vanquished by quelling the fear, once imagined and realized it is there to stay. It must also be a collectively held belief, the will of one man or woman is not enough to conjure anything. A daring hero who wishes to have a magic blade will not gain one, but if those around him or her imagine them to have one, then it becomes so.
The same goes even for the gods, if worship sours towards them then so does the god change. But that does not mean that they are any less powerful than a "real" god. Quite the opposite - they are just as dangerous, if not more so, since they can gain further power should their believers have enough faith in them.
Mortals Become Heroes
The world of Kháos is always in conflict, whether between different factions, the gods, monsters or some alien threat. Rising to meet these challenges are mortal or more-than-mortal men, heroes who best their foes with wit, athleticism or magical items. What binds them together is their shared archetypes, there's the Slayer and the Warrior; the Philosopher and the Provider, as well as many more. They are the collective tales of many heroes, presented through the lens of one.
All heroes of Kháos have to contend with the scheming gods at some point, as they have vast influence over mortal lives. Some serve as champions to their god, either chosen for great deeds or set upon before birth. Some have flourishing relationships with the gods, others see their vindictive and treacherous side.
These heroes fill important roles in Kháos' societies, as cultural touchstones, moral examples and the potential of mortals to be something greater. To be more than a passing shout into the wind.
History
History in Kháos is told in vague terms, things happened "a long time ago" or "in ages past". As such history turns quickly into legend and myth, the stories are often filled with moral preaching, idealism, romanticism, prophecy and poetry. With the gods involvement, true stories become indistinguishable from myths. Then after people start believing in those myths, the myths become real. Creating a never-ending cycle of story and truth.
In broad strokes Kháos can be separated into four distinct ages, first came the Age of Awakening, when Gods and mortals threw off the yoke of the Titans. The only memories from this age are of the Gods and the Titans and their stories. Such as of Publius who defied both the gods and titans by bringing the flame of civilization to mortal kind, for which he was at first punished by Keranos and later extolled by Ephara. Tales off Purphoros trying to steal Kruphixs' secrets or how Heliod and Iroas were tricked into dueling each other over their honor by the Titans. It ends with the defeat of the Titan Kaesar by the gods.
Second came the Age of Heroes, from whence work such as the Theriad was written. It contains the tales of the Champion of Heliod, more than a mortal the Champion is the collected version of many champions of Heliod and perhaps some that are yet to be. It is the age when mortals rose to do great deeds, slaying great beasts, founding the first Polis and creating fine works of art, poem, song and literature.
Third came the Age of War, beginning with The Akroan War, where the different burgeoning nations and Polis banded together to attack the city of Akros. The war was precipitated by the queen of Olantin abandoning her husband to marry the prince of Akros. This age is filled with tales of conflict, such as Phenaxe's escape of The Underworld at the head of a phalanx come to fight alongside the Olantian forces. In the end as prophesied by the sphinx oracle Medomai, that Olantin would fall. Even now Akros remains, whilst no one now remembers where Olantin stood. But there are brighter tales from this age, like The Callapheia, which follows the mariner Callaphe as she explored the vast oceans of Kháos. She outwitted the gods and managed to sail her ship off the edge of the world into Nyx, claiming her own space among the stars. When the Age of War ended the gods went into the Great Silence, and were not seen in Nyx, nor heard by their worshippers.
The last age, which only ended a century ago was called The False Age after the satyr Xenagos, who tried to become a god. When he tried to usurp the place of the gods they came back from the Great Silence, Heliod empowered his champion Elspeth and she struck down Xenagos before he could complete his plans. But the attacks left Kháos weakened — conflict rages in the power vacuums left behind and much of the gods' influence has weakened.
Gods
A pantheon of fifteen gods guides religious life on Kháos. From the sun and agriculture to death and passage into the Underworld, the gods oversee the forces of nature and the most important aspects of mortal life. These gods are quite real to the people of Kháos, who see them moving across the sky at night and sometimes encounter them face to face. Thus, most people perform rituals and devotions that honor various gods, hoping to win their favor and stave off their wrath. They tell and retell the stories of the gods' deeds—even as they watch those stories continue to play out in the vastness of the night sky.