Y'know, this whole "there are only two - a master and an apprentice" thing from the PT really just pisses me off. It felt like it was meant to be some throw-away line that sounded vaguely dramatic and mysterious, which also prevented the existence of a Sith army that would just absolutely eviscerate the Jedi Order if they wanted to.
For decades, people have been twisting themselves into knots trying to fit that statement into new and existing canon, where we have situations that people running around with red lightsabers really aren't true Sith, even though they practice high levels of skill in Dark Side arts, like the Inquisitors, Dooku & Ventris, Skoll & Hati (they even had blood-orange lightsabers, not full-synthetic red kyber to let us know they were never "real" Sith) - people who are-but-not-quite. It's always only ever just Palpatine and ... someone ... running around causing mass-havoc across the galaxy. Did Maul, complete with a
Dark Lord of the Si
th "Darth" title prior to Anakin/Vader, cease being a Sith after Kenobi cut him in half, recovered and went rogue?
And what of the original
ancient Sith race, the original inhabitants of Korriban, from which many "modern" Sith derive descendancy? Were there only ever just 2 of them to qualify as a whole "species" of Dark Side wielders?
IMO, Lucas did a grave disservice to the franchise by limiting "official" Sith numbers to "only two". It just never made any sense narratively, and subsequent writers, directors and producers have really had a needlessly challenging time trying to work around that absurd canon just to be able to tell interesting stories. I see people doing it here to explain the equally weird "I am ALL the Sith" statement from Palpy in the final film. How does that make sense when Rey said she was "ALL the Jedi" and they clearly didn't have the same limit in numbers, and there were still clearly Jedi running around all over the place after the GO-66 purge?
I really wish Filoni or someone would decanonize that remark, but I suspect it won't happen so long as Lucas is still around. It's buried itself too deeply in the lore at this point anyway, like an Alabama tick...