"Always two there are. No more, no less," warns sage Jedi Master Yoda of the Sith, the ancient enemy of the Jedi. "A master and an apprentice."
Kylo Ren is entrenched in the Dark Side of the Force, but the corrupted son of Han Solo and Leia Organa isn't a Sith — in fact, come The Last Jedi, the red lightsaber wielding villain wants to tear it all down: the Jedi, the Sith, the past, all of it.
Spoilers for The Last Jedi.
The Rule of Two governed the Sith for a millennium, but Kylo Ren and the mysterious Supreme Leader Snoke never identify themselves as Sith.
Snoke, who exhibits a powerful understanding of the Dark Side — including the capability to utilize Force lightning, traditionally a Sith ability — seemed to view the twisted Ben Solo, grandson of Anakin Skywalker, as little more than a tool: one to use, perhaps, to get to Luke Skywalker.
In a surprising turn of events, Kylo cuts down Snoke with Anakin's coveted lightsaber before propositioning Rey: join me, and we'll rule the galaxy. Let the past die, he tells her. Kill it, if you have to. It's an offer Rey refuses.
With Rey having made her choice — she's firmly aligned with Ben's mother, Leia, and her Resistance forces — Kylo is left to rule the First Order unchallenged and alone.
Kylo Ren's attempts to turn Rey had no basis in any kind of loyalty to the Sith or their misguided rule of two. It's something Kylo actively rejects, even as he further digs his heels into the Dark Side: it's all part of a past he wants to erase.
Kylo wants to carve a new path forward — and now that he's the newly self-appointed Supreme Leader, Kylo will stop at nothing to eradicate the hopeful Resistance and enforce his way of belief on the galaxy.
After a "duel" with Luke Skywalker — actually a projected distraction from his old Master — Kylo tried once more, in vain, to sway Rey to his side, only to be rejected. Rey is a prize for Kylo: she's an immensely powerful Force user, and as far as anyone knows, the last-surviving Jedi.
Darth Sidious had a number of underlings — Maul, Dooku, Darth Vader — and Anakin Skywalker oversaw the learnings of Jedi padawan Ahsoka Tano and, later, the nefarious actions of the imperial Inquisitorius, but a jilted Kylo Ren will rule alone.
Star Wars: The Last Jedi is now playing.