The Flashpoint Kaon Under Siege was added to Star Wars: The Old Republic with Patch 1.1 and it’s one of the hardest in the game. It’s intended for players who are at least a level 50. It takes place on a Spaceshuttle where an infection broke out, which turned everyone into a creature that resembles a zombie.
The infection was passed from one person to another until everyone was infected. The main difference between this instance and many of the others is that the mobs are much harder to kill and there are a lot of them in the beginning of the Flashpoint.