The Knights of Ren are a sect of warriors who follow the dark side of the Force, which they refer to as "the Shadow," and a philosophy known as "the Ren." Over a century ago, the Knights of Ren were destroyed by their leader, the redeemed Ben Solo, during the Battle of Exegol. However, in recent years, followers of the dark side have revived the legendary Knights as a proxy organization within the larger Sith Eternal cult.
Centuries ago, the Knights of Ren were an order of warriors who worshiped the dark side of the Force and became legendary for terrorizing the Unknown Regions. What happened to this original order of Knights is not yet known, and some scholars of galactic history even believe that they might have been a myth made up by spacers living on the edges of the Outer Rim Territories.
Around a century ago, after Luke Skywalker re-founded the Jedi Order, another group of dark-siders took up the name of the Knights of Ren and began pillaging worlds in the Outer Rim Territories, on the edges of the Unknown Regions. These Knights were led by a man named "Ren," and they simply followed wherever the dark side of the Force led them, constantly looking to expand their numbers. At some point, they came under the influence of the dark side creation Snoke, who frequently supplied them with the locations of important artifacts or dark-siders to join their ranks. Snoke was responsible for pointing the fallen Jedi Ben Solo towards the Knights and, eventually, Solo took over for Ren as Master of the Knights of Ren — taking the name "Kylo Ren" for himself and becoming Snoke's enforcer during the reign of the First Order. This iteration of the Knights ultimately were eradicated on Exegol, by the man who had been their leader, mere moments before the Sith themselves became extinct.
In the present day, the Sith Eternal cult—the spiritual successors of the Sith Order—operate in the shadows, bidding their time until it becomes necessary to reveal themselves. But patience is not a common virtue of the dark side; and some of the warriors of the cult have taken up the names of the Knights of Ren once again to sow chaos and discord more overtly in the galaxy, without specifically exposing their cult-origins.
"You don't follow me, friend. You follow this. The Ren."
The Knights of Ren follow "the Ren," an aspect of the dark side of the Force, which they refer to as "the Shadow." According to the Knights, the Ren is the true nature of the dark side: unconcerned with right or wrong, unbothered by what or whom it is burning, and without regard for ambitions or goals. The Ren just "is." It consumes all the dark side puts in its path without apology.
As a result, the Knights of Ren follow a loose code of conduct. They each live life the way they want, taking what the galaxy gives to them, consuming what the dark side sends to them, and they do so without further thought and consideration. They seek out people and places strong in the dark side of the Force, and their only rigid rule appears to be that only those Force-sensitives who can use the dark side are allowed to join them. In order to prove themselves, a candidate-Knight must kill someone meaningful to them as proof of their dedication to the Knights' cause and to the Shadow.
Members are free to follow their own ambitions, as Kylo Ren—the former leader of the Knights of Ren—sought out artifacts and places in connection with the ancient Sith and even served the First Order as the Supreme Leader's apprentice, but the Knights will also work together to conquer worlds and to recruit new members into their ranks. The Knights of Ren saw themselves as warriors of the dark side itself. They fought its battles, bathed in its power, preserved its tools (both its artifacts and its servants) through whatever means necessary.
I went ahead and moved the roster portion, since this is an article for the overall religion and won't be a tracker for those that follow it, that would likely find a better home on the SE subforum. Other than that,