Kelx is a religion whose followers believe that the whole world is in the mind of a man condemned to die. (pg 467 Anathem)
The religion was created in the Sixteenth or Seventeenth Century A.R. The Kelx believe that Arbre exists in a chain of universes, each one creating the next. They believe that in the universe preceding Arbre's, there was once a highwayman. This criminal waylaid a family of three, a father, mother and a little girl. The father, he slew outright. The mother, he raped and then murdered. The child, he took as a hostage to hold law enforcement at bay. Eventually cornered, he strangled the child to eliminate a potential witness. The Kelx know this unfortunate child as the Innocent. The bandit was tried, convicted and sentenced to die, placed in a cell to await his fate. The Kelx therefore name this highwayman the Condemned Man. The Condemned Man spent an indeterminate, yet very long time in prison, contemplating his crimes. After a time - "half of his life", the story claims - the Condemned Man was brought before a judge, whom the Kelx name the Magistrate. The Magistrate gave the Condemned Man one last chance to plead for his life, to explain to the court why he should not be put to death.
The Condemned Man admitted his sins, and suggested that the greatest of them all was the murder of the Innocent. He argued that each human being has within them the ability to create - a song, a poem, a book, even a world - and that when we kill a person, we kill everything they would ever have created. Therefore, each of his murders was a crime of literally cosmic proportions. But the murder of the Innocent was the greatest, for she was the youngest and had the most time left in which to create. However, by this same token, he should not be put to death, nor should anyone be put to death, for he, too, had the ability to create worlds. Just as it had been a crime for him to murder the Innocent and all she would ever have created, it would be an abomination to kill the Condemned Man and all he would ever create. (pg 476 Anathem) The Magistrate expressed great skepticism that the Condemned Man truly had it in him to create an entirely world, and challenged the Condemned Man to prove his argument. So the Condemned Man began to speak of another world. This world that the Condemned Man created was Arbre. As he told the story, however, he found it unavoidable to speak of problems, such as wars, famines and plagues - and every time he solved one, his solution would ultimately create another. At the end of the day's proceedings, the Magistrate was not wholly convinced of the Condemned Man's reasoning, but also unable to wholly dismiss it. So, he adjourned, and gave the Condemned Man another day to prove his case. But he cautioned the Condemned Man that he could not see the world the Man was creating as being any better or worse than the world they lived in. If the Condemned Man sought to prove his case, he would need to create not just a world, but a better one.
The Kelx believe that the trial continues even now, with the Condemned Man relating the story of Arbre to the Magistrate. Each day, he relates more of the tale - and each day comes to the same end, with the Magistrate allowing the Condemned Man another day to make his case. Yet they believe that, one way or another the trial must someday end. The Magistrate cannot indulge the Condemned Man forever; he must eventually render a judgment and a sentence. If the Condemned Man has created a basically decent, good world, the Magistrate will accept his argument and spare him, but if he cannot do so, the Magistrate will send him to the gallows. If he is executed, then he will stop creating and Arbre will stop existing, but if he is spared, the story of Arbre will continue.The Kelx believe that it is possible for the people of Arbre to influence the story the Condemned Man tells - that he is, in a sense, recounting their actions rather than authoring them himself. It is therefore up to each and every resident of Arbre to behave in a good and decent manner, to enable the Condemned Man to tell a story that will impress the Magistrate, and eventually persuade him to spare the Condemned Man from the hangman's knot.
The Kelx religion is analagous in some ways to the Jehovah's Witnesses on Earth. The Kelx believe they must evangelize to convert others to their faith. The Jehovah's Witnesses believe that we are participants in a challenge involving the competing claims of Jehovah and Satan to universal sovereignty.
The central story of the Kelx is similar to One Thousand and One Nights, in that Scheherazade must tell a story to her husband each night to avoid execution.
While making his voyage on an ice-breaker ship, Fraa Erasmus attends a Kelx service led by Magister Sark.
The Kelx religion uses strong triangle iconography, with the Condemned Man, the Innocent and the Magistrate each represented by one vertex, or corner, of the triangle, and the relationship between each symbolized by the sides.