From the introduction:
Welcome to Kisarta, a setting of damned souls and otherworldly horrors for the 5th Edition of the world’s most famous RPG! You will stand before dangerous creatures straight from a nightmare, terrifying and forbidden knowledge, and ancient secrets which might lead you to insanity. But the true question is: what is Kisarta?
It is the Pale Sun that shines dim over each of the Dominions you will explore during your travels.
It is the centerpiece riddle, the key to everything.
It is the crux of the Great Game, that is to say, the complex plot weaved by the local gods.
It is a universe of its own, where life and death, purity and corruption, hope and despair bleed together in tangled and contradictory schemes, while hoping to give meaning to a dull and dying existence.
Exploring Kisarta means not only traveling through places full of dangers, but also walking in search of the meaning of your own existence, in the shadows of the strange and awesome powers of these lands which might be crucial to your success, or failure. Your weapons will be not only literal weapons and arcane spells, but also forgotten lore, pacts with unfathomable beings and your skill in navigating the intrigues of these dark corridors of powers.
The true rule is that there are no rules, only plans of distant deities, whose designs are alien to mortal minds.
So prepare yourselves and pray for your salvation, since in these lands you will find neither hope nor pity.