Suprisingly, upon returning to the Citadel (again!), I found very few new sideqests to distract me, so I decided that it would be a good time to do “Bring Down the Sky,” Mass Effect's only story-based DLC. The whole thing takes between 1-2 hours to complete, has some new enemies (although none that actually exhibit new behavior), and the best vehicle combat anywhere in the game. The mission also goes out of its way to give you some nice equipment and decisions that alter the outcome of the mission. It's honestly quite good and worth the price of admission (Free on PC).