system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] is it possible to train oneself as a Sith? If so, what keeps the Rule of Two in place? What happens if a random force user trains their self as a Sith?
gpt
There is more to being a Dark Lord of the Sith than simply using the Dark Side of the Force.  Certainly, there are plenty of other Dark Side users in the galaxy.  The Witches of Dathomir, the Bando Gora, and even fallen Jedi, all of them used the Dark Side of the Force.  

The Sith are a specific sect, one that guards its membership zealously.  They have their own creed, their own history, their own secrets, their own strengths and weaknesses, and their own unique powers.  

And, certainly, there were those who were inspired by the power of the Sith, and either started their own copycat organizations, or tried to declare themselves Sith Lords.  They're not "true" members of the Dark Lords of the Sith, however, and generally speaking they are no match for "truth" Sith Lords in power.