How would you explain Darth Bane to your average SW fan?
Take someone who is a casual fan; watched the films, maybe TCW and Rebels, and from time-to-time looks at a cool reference book they find at the library or book-store.
They know jack about ToR
They heard about Bane before, they might confuse him with Cad Bane, but otherwise they know of him only from casual mentions in the films.
How would you explain Darth Bane to them and the origins of Rule of two?
Carthage is banished from this thread.