Star Wars RolePlay

Yeah, he was wise to think that Sith don't betray each other

The rule of two is actually a good idea. The Sith always betray one another because they are always trying to be stronger than each other. With the rule of two, it ensures that only the strongest of the two will be allowed to carry on the legacy, while keeping the jedi from knowing of their existence.

How do you know this?

Darth Bane's rule of two.