Near the end of Star Wars Episode IX: The Rise of Skywalker there are several hooded figures that are shown chanting stuff (in Sith?) and just hanging out with Palpatine. Who were these people?
They seem to have been the "Sith Eternal", a cultist order who followed the Sith, according to the Visual Dictionary. They're mentioned earlier in the movie as "Sith Loyalists" and helped build the Final Order fleet.