Operation Nightmare is currently available with the latest update of Star Wars: The Old Republic, and this means unpleasant-sounding "Nightmare Mode" in Terror From Beyond. That's pretty much as it sounds: a tricky level 55 challenge: "The fight to seize control of the Gree Hypergate will leave you gasping for breath as you battle the five main bosses, now amped up to challenge even the most skilled group of players!" There's also a bunch of guild features and similar things included in this update. Later on Nightmare Mode will also be applied to Legion Of Scum & Villainy, for extra scummy and villainous difficulties.
The trailer for all this is far, far away, and a long time ago, etc.