The Champion of Mustafar questline was introduced as one of the two main quest arcs for Mustafar with Publish 1.0.
It begins simply enough, but eventually leads the player to uncover and thwart a plan to destroy the very planet itself. The series of quests takes place all over the volcanic planet of Mustafar, in ancient Old Republic ruins, and even in the central volcano itself. It contains mass battles, team-puzzles, and lots of exploration. The first few quests can be solo'd, but a group is required in later quests.