Knights of Ren

The Knights of Ren are an organization introduced in the Star Wars sequel trilogy. Kylo Ren is a high-ranking member of this group and is considered a master among the knights, primarily by Snoke. Despite their alliance with the First Order, the Knights of Ren are not part of the formal hierarchy of the organization, as their agendas trumped that of the First Order's commanding officers. It is currently unknown how many Knights of Ren exist, but including Kylo Ren, seven have been seen so far.

Organization
The Knights of Ren include Kylo Ren, whom Supreme Leader Snoke refers to as a master of the Knights of Ren. As a member of the Knights of Ren, Kylo is not officially part of the hierarchy of the First Order. Despite this, he operates freely within the order, who tolerate his presence with some hesitation as his agenda does not strictly coincide with their own. Kylo wears a black and silver helmet and garb similar to the battle gear worn by the other Knights of Ren.

Knights of Ren ranks

 * Master of the Knights of Ren: Presumably, Master of the Knights of Ren is a rank granted to the highest ranking member of the Knights, like Kylo Ren.

Knights of Ren titles

 * Ren: Presumably, all members of the Knights of Ren are addressed by the title of Ren, after they are addressed by their Knight names.

History
The Knights of Ren operated in the decades following the Galactic Civil War. They are under the command of Supreme Leader Snoke, who used them as a tool of the Dark side of the Force, alongside the First Order. Approximately six years after the Jedi massacre, the Knights of Ren, particularly Kylo Ren, under the orders of Snoke, were to find and kill Luke Skywalker (one of the last surviving member of the New Jedi Order and the last surviving Jedi Master in the galaxy), as Snoke knew that as long as Luke lived, a new generation of Jedi Knights could rise again.

Notable Knights

 * Snoke
 * Kylo Ren
 * Seven other in individuals with the name "Ren"

The Force Awakens
In the sequel trilogy, the Knights of Ren are the newest threat to the Republic and subordinates to the First Order. Snoke serves as their leader, with Kylo Ren in turn leading under him, as he refers to Kylo as "Master of the Knights of Ren" in the film. They appear in a vision Rey had on Takodana, in which they are revealed to be responsible for destroying the fledgling Jedi Order that Luke Skywalker had tried to rebuilt, their Jedi Temple, and an unnamed Jedi Knight.

The Last Jedi
Though they do not appear in the film physically, it is revealed by Luke Skywalker to Rey that the Knights of Ren were Luke's other apprentices that saw fit to join Kylo Ren and slaughter the rest of their fellow Jedi students in Luke's Jedi temple.

Trivia

 * The "Ren" surname is similar to the title of "Darth" used by the members of the Sith Order, however, unlike the Sith, the members of the Knights of Ren are addressed by their Knight names, before being addressed by the Ren surname.
 * The Knights of Ren were originally slated to appear in The Last Jedi, but were cut due to their role being filled by the Praetorian Guards. Furthermore, director Rian Johnson disliked the idea of the Knights of Ren dying shortly after their first appearance were they to appear the the film.