Rule of Three

The Rule of Three doctrine is the guiding principle of the Four Sith. The Rule of Three was instituted by Darth Shuigang. This transfer of power would only take place when the Apprentice takes their Master's life and finds a worthy student to repeat the cycle, this way the Sith will grow more powerful and still exist through the new Master. Both Master and Apprentice were considered to be Sith Lords.